tests: fully type the test suite (#2794)

* tests: fully type the test suite

* chore: require more typing

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

cibuildwheel/__main__.py

@@ -52,7 +52,7 @@ class Unbuffered:
         self.stream.writelines(data)
         self.stream.flush()
 
-    def __getattr__(self, attr: str) -> Any:
+    def __getattr__(self, attr: str) -> Any:  # noqa: ANN401
         return getattr(self.stream, attr)
 
 

cibuildwheel/environment.py

@@ -131,7 +131,7 @@ class ParsedEnvironment:
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({[repr(a) for a in self.assignments]!r})"
 
-    def options_summary(self) -> Any:
+    def options_summary(self) -> list[EnvironmentAssignment]:
         return self.assignments
 
 

cibuildwheel/options.py

@@ -987,8 +987,8 @@ class Options:
     def option_summary(
         self,
         option_name: str,
-        option_value: Any,
-        default_value: Any,
+        option_value: Any,  # noqa: ANN401
+        default_value: Any,  # noqa: ANN401
         overrides: Mapping[str, Any] | None = None,
         skip_unset: bool = False,
     ) -> str | None:
@@ -1040,7 +1040,7 @@ class Options:
             return value
 
     @staticmethod
-    def option_summary_value(option_value: Any) -> str:
+    def option_summary_value(option_value: Any) -> str:  # noqa: ANN401
         if hasattr(option_value, "options_summary"):
             option_value = option_value.options_summary()
 

cibuildwheel/selector.py

@@ -2,7 +2,7 @@ import dataclasses
 import itertools
 from enum import StrEnum
 from fnmatch import fnmatch
-from typing import Any, Self
+from typing import Self
 
 import bracex
 from packaging.specifiers import SpecifierSet
@@ -113,7 +113,7 @@ class BuildSelector:
 
         return should_build and not should_skip
 
-    def options_summary(self) -> Any:
+    def options_summary(self) -> dict[str, str | list[str]]:
         return {
             "build_config": self.build_config,
             "skip_config": self.skip_config,
@@ -134,5 +134,5 @@ class TestSelector:
         should_skip = selector_matches(self.skip_config, build_id)
         return not should_skip
 
-    def options_summary(self) -> Any:
+    def options_summary(self) -> dict[str, str]:
         return {"skip_config": self.skip_config}

cibuildwheel/util/packaging.py

@@ -2,7 +2,7 @@ import shlex
 from collections.abc import Mapping, Sequence
 from dataclasses import dataclass, field
 from pathlib import Path, PurePath
-from typing import Any, Literal, Self, TypeVar
+from typing import Literal, Self, TypeVar
 
 from packaging.utils import parse_wheel_filename
 
@@ -102,7 +102,7 @@ class DependencyConstraints:
 
         return None
 
-    def options_summary(self) -> Any:
+    def options_summary(self) -> str | dict[str, str]:
         if self == DependencyConstraints.pinned():
             return "pinned"
         elif self.packages:

docs/main.py

@@ -8,7 +8,7 @@ import rich.console
 import rich.text
 
 
-def define_env(env: Any) -> None:
+def define_env(env: Any) -> None:  # noqa: ANN401
     "Hook function for mkdocs-macros"
 
     @env.macro  # type: ignore[untyped-decorator]

pyproject.toml

@@ -129,14 +129,9 @@ files = [
 ]
 warn_unused_configs = true
 strict = true
-disallow_untyped_defs = false
 enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
 warn_unreachable = false
 
-[[tool.mypy.overrides]]
-module = "cibuildwheel.*"
-disallow_untyped_defs = true
-
 [[tool.mypy.overrides]]
 module = [
     "setuptools._distutils", # needed even if only directly import setuptools._distutils.util
@@ -196,6 +191,7 @@ extend-select = [
   "B",           # flake8-bugbear
   "I",           # isort
   "ARG",         # flake8-unused-arguments
+  "ANN",         # flake8-annotations
   "C4",          # flake8-comprehensions
   "EM",          # flake8-errmsg
   "ICN",         # flake8-import-conventions
@@ -236,6 +232,8 @@ ignore = [
 ]
 flake8-unused-arguments.ignore-variadic-names = true
 flake8-tidy-imports.ban-relative-imports = "all"
+flake8-annotations.allow-star-arg-any = true
+flake8-annotations.mypy-init-return = true
 
 [tool.ruff.lint.flake8-tidy-imports.banned-api]
 "typing.Mapping".msg = "Use collections.abc.Mapping instead."

test/conftest.py

@@ -46,7 +46,7 @@ def pytest_addoption(parser: pytest.Parser) -> None:
     )
 
 
-def pytest_configure(config):
+def pytest_configure(config: pytest.Config) -> None:
     flag_enable = config.getoption("--enable")
     flag_platform = config.getoption("--platform")
 

test/test_0_basic.py

@@ -1,4 +1,5 @@
 import textwrap
+from pathlib import Path
 
 import packaging.utils
 import pytest
@@ -21,7 +22,7 @@ basic_project = test_projects.new_c_project(
 
 
 @pytest.mark.serial
-def test_dummy_serial():
+def test_dummy_serial() -> None:
     """A no-op test to ensure that at least one serial test is always found.
 
     Without this no-op test, CI fails on CircleCI because no serial tests are
@@ -29,7 +30,9 @@ def test_dummy_serial():
     """
 
 
-def test(tmp_path, build_frontend_env, capfd):
+def test(
+    tmp_path: Path, build_frontend_env: dict[str, str], capfd: pytest.CaptureFixture[str]
+) -> None:
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 
@@ -52,7 +55,7 @@ def test(tmp_path, build_frontend_env, capfd):
 
 
 @pytest.mark.skip(reason="to keep test output clean")
-def test_sample_build(tmp_path, capfd):
+def test_sample_build(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 
@@ -70,7 +73,9 @@ def test_sample_build(tmp_path, capfd):
 @pytest.mark.parametrize(
     "enable_setting", ["", "cpython-prerelease", "pypy", "cpython-freethreading"]
 )
-def test_build_identifiers(tmp_path, enable_setting, monkeypatch):
+def test_build_identifiers(
+    tmp_path: Path, enable_setting: str, monkeypatch: pytest.MonkeyPatch
+) -> None:
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 
@@ -93,7 +98,9 @@ def test_build_identifiers(tmp_path, enable_setting, monkeypatch):
         (None, {"CIBW_ALLOW_EMPTY": "1"}),
     ],
 )
-def test_allow_empty(tmp_path, add_args, env_allow_empty):
+def test_allow_empty(
+    tmp_path: Path, add_args: list[str] | None, env_allow_empty: dict[str, str]
+) -> None:
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 

test/test_abi_variants.py

@@ -1,4 +1,7 @@
 import textwrap
+from pathlib import Path
+
+import pytest
 
 from . import test_projects, utils
 
@@ -31,7 +34,7 @@ limited_api_project = test_projects.new_c_project(
 limited_api_project.files["pyproject.toml"] = pyproject_toml
 
 
-def test_abi3(tmp_path):
+def test_abi3(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     limited_api_project.generate(project_dir)
 
@@ -178,7 +181,7 @@ ctypes_project.files["test/add_test.py"] = textwrap.dedent(
 ctypes_project.files["pyproject.toml"] = pyproject_toml
 
 
-def test_abi_none(tmp_path, capfd):
+def test_abi_none(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     project_dir = tmp_path / "project"
     ctypes_project.generate(project_dir)
 

test/test_android.py

@@ -2,6 +2,8 @@ import os
 import platform
 import re
 import sys
+import typing
+from collections.abc import Callable
 from dataclasses import dataclass
 from pathlib import Path
 from shutil import rmtree, which
@@ -52,8 +54,10 @@ if "ANDROID_HOME" not in os.environ:
 # Many CI services don't support running the Android emulator: see platforms.md.
 supports_emulator = (not ci) or ("GITHUB_ACTIONS" in os.environ and platform.system() == "Linux")
 
+T = typing.TypeVar("T", bound=Callable[..., typing.Any])
 
-def needs_emulator(test):
+
+def needs_emulator(test: T) -> T:
     # All copies of the testbed app run on the same emulator with the same
     # application ID, so these tests must be run serially.
     test = pytest.mark.serial(test)
@@ -85,7 +89,7 @@ cp313_env = {
 }
 
 
-def test_android_home(tmp_path, capfd):
+def test_android_home(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     new_c_project().generate(tmp_path)
     env = os.environ.copy()
     del env["ANDROID_HOME"]
@@ -100,7 +104,7 @@ def test_android_home(tmp_path, capfd):
 # a build, which is marked as serial so it will run before the parallel tests, but isn't
 # marked as needs_emulator so it will run on all CI platforms.
 @pytest.mark.serial
-def test_expected_wheels(tmp_path, spam_env):
+def test_expected_wheels(tmp_path: Path, spam_env: dict[str, str]) -> None:
     # Since this test covers all Python versions, check the cross venv.
     test_module = "_cross_venv_test_android"
     project = new_c_project(setup_py_add=f"import {test_module}")
@@ -119,7 +123,7 @@ def test_expected_wheels(tmp_path, spam_env):
 
 
 @needs_emulator
-def test_frontend_good(tmp_path, build_frontend_env):
+def test_frontend_good(tmp_path: Path, build_frontend_env: dict[str, str]) -> None:
     new_c_project().generate(tmp_path)
     wheels = cibuildwheel_run(
         tmp_path,
@@ -129,7 +133,7 @@ def test_frontend_good(tmp_path, build_frontend_env):
 
 
 @pytest.mark.parametrize("frontend", ["pip"])
-def test_frontend_bad(frontend, tmp_path, capfd):
+def test_frontend_bad(frontend: str, tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     new_c_project().generate(tmp_path)
     with pytest.raises(CalledProcessError):
         cibuildwheel_run(
@@ -140,7 +144,7 @@ def test_frontend_bad(frontend, tmp_path, capfd):
 
 
 @needs_emulator
-def test_archs(tmp_path, capfd):
+def test_archs(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     new_c_project().generate(tmp_path)
 
     # Build all architectures while checking the handling of the `before` commands.
@@ -189,7 +193,7 @@ def test_archs(tmp_path, capfd):
         pytest.fail(f"Unexpected line: {line!r}")
 
 
-def test_build_requires(tmp_path, capfd):
+def test_build_requires(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     # Build-time requirements should be installed for the build platform, not for Android. Prove
     # this by installing some non-pure-Python requirements and using them in setup.py.
     #
@@ -226,13 +230,13 @@ def test_build_requires(tmp_path, capfd):
 
 
 @pytest.fixture
-def spam_env(tmp_path):
+def spam_env(tmp_path: Path) -> dict[str, str]:
     project = new_c_project()
     project.files["test_spam.py"] = dedent(
         """\
         import spam
 
-        def test_spam():
+        def test_spam() -> None:
             assert spam.filter("ham")
             assert not spam.filter("spam")
             print("Spam test passed")
@@ -240,7 +244,7 @@ def spam_env(tmp_path):
     )
     project.files["test_empty.py"] = dedent(
         """\
-        def test_empty():
+        def test_empty() -> None:
             pass
         """
     )
@@ -265,7 +269,13 @@ def spam_env(tmp_path):
         ("pytest test_spam.py", "=== 1 passed in "),
     ],
 )
-def test_test_command_good(command, expected_output, tmp_path, spam_env, capfd):
+def test_test_command_good(
+    command: str,
+    expected_output: str,
+    tmp_path: Path,
+    spam_env: dict[str, str],
+    capfd: pytest.CaptureFixture[str],
+) -> None:
     cibuildwheel_run(tmp_path, add_env={**spam_env, "CIBW_TEST_COMMAND": command})
     stdout, stderr = capfd.readouterr()
     assert expected_output in stdout
@@ -300,7 +310,13 @@ BAD_PLACEHOLDER_ERROR = (
         ("pytest test_ham.py", "not found: test_ham.py"),
     ],
 )
-def test_test_command_bad(command, expected_output, tmp_path, spam_env, capfd):
+def test_test_command_bad(
+    command: str,
+    expected_output: str,
+    tmp_path: Path,
+    spam_env: dict[str, str],
+    capfd: pytest.CaptureFixture[str],
+) -> None:
     with pytest.raises(CalledProcessError):
         cibuildwheel_run(tmp_path, add_env={**spam_env, "CIBW_TEST_COMMAND": command})
     assert expected_output in capfd.readouterr().err
@@ -314,7 +330,9 @@ def test_test_command_bad(command, expected_output, tmp_path, spam_env, capfd):
         ("-E", 1),
     ],
 )
-def test_test_command_python_options(options, expected, tmp_path, capfd):
+def test_test_command_python_options(
+    options: str, expected: int, tmp_path: Path, capfd: pytest.CaptureFixture[str]
+) -> None:
     project = new_c_project()
     project.generate(tmp_path)
 
@@ -330,7 +348,9 @@ def test_test_command_python_options(options, expected, tmp_path, capfd):
 
 
 @needs_emulator
-def test_package_subdir(tmp_path, spam_env, capfd):
+def test_package_subdir(
+    tmp_path: Path, spam_env: dict[str, str], capfd: pytest.CaptureFixture[str]
+) -> None:
     spam_paths = list(tmp_path.iterdir())
     package_dir = tmp_path / "package"
     package_dir.mkdir()
@@ -345,7 +365,7 @@ def test_package_subdir(tmp_path, spam_env, capfd):
 
 
 @needs_emulator
-def test_no_test_sources(tmp_path, capfd):
+def test_no_test_sources(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     new_c_project().generate(tmp_path)
     with pytest.raises(CalledProcessError):
         cibuildwheel_run(
@@ -359,17 +379,17 @@ def test_no_test_sources(tmp_path, capfd):
 
 
 @needs_emulator
-def test_environment_markers(tmp_path):
+def test_environment_markers(tmp_path: Path) -> None:
     project = new_c_project()
     test_filename = "test_environment_markers.py"
     project.files[test_filename] = dedent(
         """\
         import pytest
 
-        def test_android():
+        def test_android() -> None:
             import certifi
 
-        def test_not_android():
+        def test_not_android() -> None:
             try:
                 import platformdirs
             except ImportError:
@@ -392,7 +412,7 @@ def test_environment_markers(tmp_path):
 
 
 @needs_emulator
-def test_verbosity(tmp_path, capfd):
+def test_verbosity(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     new_c_project().generate(tmp_path)
     test_env = {
         **cp313_env,
@@ -418,7 +438,7 @@ def test_verbosity(tmp_path, capfd):
 
 
 @needs_emulator
-def test_api_level(tmp_path, capfd):
+def test_api_level(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     project = new_c_project()
     project.files["pyproject.toml"] = dedent(
         """\
@@ -450,7 +470,7 @@ def test_api_level(tmp_path, capfd):
 
 
 @needs_emulator
-def test_libcxx(tmp_path, capfd):
+def test_libcxx(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     project_dir = tmp_path / "project"
     output_dir = tmp_path / "output"
 
@@ -499,7 +519,7 @@ def test_libcxx(tmp_path, capfd):
 
 
 @needs_emulator
-def test_setuptools_rust(tmp_path, capfd):
+def test_setuptools_rust(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """
     Test Android cross-compilation using the setuptools-rust toolchain.
     """
@@ -584,7 +604,7 @@ def test_setuptools_rust(tmp_path, capfd):
 
 
 @needs_emulator
-def test_maturin(tmp_path, capfd):
+def test_maturin(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """
     Test Android cross-compilation using the maturin backend.
     """

test/test_before_all.py

@@ -1,5 +1,6 @@
 import subprocess
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -29,7 +30,7 @@ project_with_before_build_asserts = test_projects.new_c_project(
 )
 
 
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_before_build_asserts.generate(project_dir)
 
@@ -61,7 +62,7 @@ def test(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_failing_command(tmp_path):
+def test_failing_command(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     test_projects.new_c_project().generate(project_dir)
 
@@ -75,7 +76,7 @@ def test_failing_command(tmp_path):
         )
 
 
-def test_cwd(tmp_path):
+def test_cwd(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     test_projects.new_c_project().generate(project_dir)
 

test/test_before_build.py

@@ -1,5 +1,6 @@
 import subprocess
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -36,7 +37,7 @@ project_with_before_build_asserts = test_projects.new_c_project(
 )
 
 
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_before_build_asserts.generate(project_dir)
 
@@ -65,7 +66,7 @@ def test(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_failing_command(tmp_path):
+def test_failing_command(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     test_projects.new_c_project().generate(project_dir)
 
@@ -79,7 +80,7 @@ def test_failing_command(tmp_path):
         )
 
 
-def test_cwd(tmp_path):
+def test_cwd(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     test_projects.new_c_project().generate(project_dir)
 

test/test_before_test.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 from . import test_projects, utils
 
 before_test_project = test_projects.new_c_project()
@@ -11,7 +13,7 @@ PROJECT_DIR = Path(__file__).parent.parent.resolve()
 
 
 class TestBeforeTest(TestCase):
-    def test_version(self):
+    def test_version(self) -> None:
         # assert that the Python version as written to pythonversion_bt.txt in the CIBW_BEFORE_TEST step
         # is the same one as is currently running.
         # because of use symlinks in MacOS run this test is also need
@@ -20,7 +22,7 @@ class TestBeforeTest(TestCase):
         print('sys.version', sys.version)
         assert stored_version == sys.version
 
-    def test_prefix(self):
+    def test_prefix(self) -> None:
         # check that the prefix also was written
         stored_prefix = PROJECT_DIR.joinpath('pythonprefix_bt.txt').read_text()
         print('stored_prefix', stored_prefix)
@@ -32,7 +34,7 @@ class TestBeforeTest(TestCase):
 """
 
 
-def test(tmp_path, build_frontend_env):
+def test(tmp_path: Path, build_frontend_env: dict[str, str]) -> None:
     project_dir = tmp_path / "project"
     before_test_project.generate(project_dir)
     test_project_dir = project_dir / "dependency"

test/test_build_frontend_args.py

@@ -1,4 +1,5 @@
 import subprocess
+from pathlib import Path
 
 import pytest
 
@@ -12,7 +13,9 @@ from . import test_projects, utils
         "build",
     ],
 )
-def test_build_frontend_args(tmp_path, capfd, frontend_name):
+def test_build_frontend_args(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str], frontend_name: str
+) -> None:
     project = test_projects.new_c_project()
     project_dir = tmp_path / "project"
     project.generate(project_dir)

test/test_build_skip.py

@@ -1,4 +1,5 @@
 import textwrap
+from pathlib import Path
 
 from . import test_projects, utils
 
@@ -15,7 +16,7 @@ project_with_skip_asserts = test_projects.new_c_project(
 )
 
 
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_skip_asserts.generate(project_dir)
 

test/test_container_engine.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 import pytest
 
 from . import test_projects, utils
@@ -5,7 +7,9 @@ from . import test_projects, utils
 basic_project = test_projects.new_c_project()
 
 
-def test_podman(tmp_path, capfd, request):
+def test_podman(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str], request: pytest.FixtureRequest
+) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the test is only relevant to the linux build")
 
@@ -35,7 +39,7 @@ def test_podman(tmp_path, capfd, request):
     assert "test log statement from before-all" in captured.out
 
 
-def test_create_args(tmp_path, capfd):
+def test_create_args(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the test is only relevant to the linux build")
 

test/test_container_images.py

@@ -1,5 +1,6 @@
 import platform
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -22,7 +23,7 @@ dockcross_only_project = test_projects.new_c_project(
 
 
 @pytest.mark.usefixtures("docker_cleanup")
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the test is only relevant to the linux build")
     if platform.machine() not in ["x86_64", "i686"]:

test/test_cpp_standards.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 import jinja2
 
 from . import utils
@@ -52,7 +54,7 @@ cpp_test_project.files["setup.py"] = jinja2.Template(setup_py_template)
 cpp_test_project.files["spam.cpp"] = jinja2.Template(spam_cpp_template)
 
 
-def test_cpp11(tmp_path):
+def test_cpp11(tmp_path: Path) -> None:
     # This test checks that the C++11 standard is supported
     project_dir = tmp_path / "project"
     cpp11_project = cpp_test_project.copy()
@@ -68,7 +70,7 @@ def test_cpp11(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_cpp14(tmp_path):
+def test_cpp14(tmp_path: Path) -> None:
     # This test checks that the C++14 standard is supported
     project_dir = tmp_path / "project"
     cpp14_project = cpp_test_project.copy()
@@ -84,7 +86,7 @@ def test_cpp14(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_cpp17(tmp_path):
+def test_cpp17(tmp_path: Path) -> None:
     # This test checks that the C++17 standard is supported
     project_dir = tmp_path / "project"
     cpp17_project = cpp_test_project.copy()

test/test_custom_repair_wheel.py

@@ -1,6 +1,7 @@
 import subprocess
 import textwrap
 from contextlib import nullcontext as does_not_raise
+from pathlib import Path
 
 import pytest
 
@@ -30,7 +31,7 @@ shutil.copy(wheel, dest)
 """
 
 
-def test(tmp_path, capfd):
+def test(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     # this test checks that a generated wheel name shall be unique in a given cibuildwheel run
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
@@ -68,7 +69,7 @@ def test(tmp_path, capfd):
     ],
     ids=["no-placeholder", "package-placeholder", "project-placeholder"],
 )
-def test_repair_wheel_command_structure(tmp_path, repair_command):
+def test_repair_wheel_command_structure(tmp_path: Path, repair_command: str) -> None:
     project_dir = tmp_path / "project"
     project = test_projects.new_c_project()
     project.files["repair.py"] = textwrap.dedent("""

test/test_dependency_versions.py

@@ -36,7 +36,9 @@ for name, expected_version in expected_versions.items():
 """
 
 
-def test_check_versions_script(tmp_path, build_frontend_env_nouv, capfd):
+def test_check_versions_script(
+    tmp_path: Path, build_frontend_env_nouv: dict[str, str], capfd: pytest.CaptureFixture[str]
+) -> None:
     if utils.get_platform() == "linux":
         pytest.skip("we don't test dependency versions on linux, refer to other tests")
 
@@ -76,7 +78,9 @@ def get_versions_from_constraint_file(constraint_file: Path) -> dict[str, str]:
 
 
 @pytest.mark.parametrize("python_version", ["3.8", "3.12"])
-def test_pinned_versions(tmp_path, python_version, build_frontend_env_nouv):
+def test_pinned_versions(
+    tmp_path: Path, python_version: str, build_frontend_env_nouv: dict[str, str]
+) -> None:
     if utils.get_platform() == "linux":
         pytest.skip("linux doesn't pin individual tool versions, it pins manylinux images instead")
     if python_version != "3.12" and utils.get_platform() == "pyodide":
@@ -127,7 +131,9 @@ def test_pinned_versions(tmp_path, python_version, build_frontend_env_nouv):
 
 
 @pytest.mark.parametrize("method", ["inline", "file"])
-def test_dependency_constraints(method, tmp_path, build_frontend_env_nouv):
+def test_dependency_constraints(
+    method: str, tmp_path: Path, build_frontend_env_nouv: dict[str, str]
+) -> None:
     if utils.get_platform() == "linux":
         pytest.skip("linux doesn't pin individual tool versions, it pins manylinux images instead")
 

test/test_emulation.py

@@ -1,5 +1,6 @@
 import itertools
 import subprocess
+from pathlib import Path
 
 import pytest
 
@@ -10,13 +11,13 @@ project_with_a_test = test_projects.new_c_project()
 project_with_a_test.files["test/spam_test.py"] = r"""
 import spam
 
-def test_spam():
+def test_spam() -> None:
     assert spam.filter("spam") == 0
     assert spam.filter("ham") != 0
 """
 
 
-def test(tmp_path, request):
+def test(tmp_path: Path, request: pytest.FixtureRequest) -> None:
     archs = request.config.getoption("--run-emulation")
     if archs is None:
         pytest.skip("needs --run-emulation option to run")
@@ -45,7 +46,7 @@ def test(tmp_path, request):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_setting_arch_on_other_platforms(tmp_path, capfd):
+def test_setting_arch_on_other_platforms(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     if utils.get_platform() == "linux":
         pytest.skip("this test checks the behaviour on platforms other than linux")
 

test/test_environment.py

@@ -2,6 +2,7 @@ import os
 import subprocess
 import sys
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -33,7 +34,7 @@ project_with_environment_asserts = test_projects.new_c_project(
 )
 
 
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     python_echo = f"'{sys.executable}' -c \"import sys; print(*sys.argv[1:])\""
     project_dir = tmp_path / "project"
     project_with_environment_asserts.generate(project_dir)
@@ -55,7 +56,7 @@ def test(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_overridden_path(tmp_path, capfd):
+def test_overridden_path(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     project_dir = tmp_path / "project"
     output_dir = tmp_path / "output"
 
@@ -108,7 +109,7 @@ def test_overridden_path(tmp_path, capfd):
         ),
     ],
 )
-def test_overridden_pip_constraint(tmp_path, build_frontend):
+def test_overridden_pip_constraint(tmp_path: Path, build_frontend: str) -> None:
     """
     Verify that users can use PIP_CONSTRAINT to specify a specific version of
     a build-system.requires dependency, by asserting the version of pytz in the

test/test_from_sdist.py

@@ -6,6 +6,8 @@ from collections.abc import Mapping
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
+import pytest
+
 from test.test_projects.base import TestProject
 
 from . import test_projects, utils
@@ -59,7 +61,7 @@ def cibuildwheel_from_sdist_run(
 # tests
 
 
-def test_simple(tmp_path):
+def test_simple(tmp_path: Path) -> None:
     basic_project = test_projects.new_c_project()
 
     # make an sdist of the project
@@ -87,7 +89,7 @@ def test_simple(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_external_config_file_argument(tmp_path, capfd):
+def test_external_config_file_argument(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     basic_project = test_projects.new_c_project()
 
     # make an sdist of the project
@@ -118,7 +120,7 @@ def test_external_config_file_argument(tmp_path, capfd):
     assert "test log statement from before-all" in captured.out
 
 
-def test_config_in_pyproject_toml(tmp_path, capfd):
+def test_config_in_pyproject_toml(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     # make a project with a pyproject.toml
     project = test_projects.new_c_project()
     project.files["pyproject.toml"] = textwrap.dedent(
@@ -145,7 +147,7 @@ def test_config_in_pyproject_toml(tmp_path, capfd):
     assert "test log statement from before-build 8419" in captured.out
 
 
-def test_internal_config_file_argument(tmp_path, capfd):
+def test_internal_config_file_argument(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     # make a project with a config file inside
     project = test_projects.new_c_project(
         setup_cfg_add="include_package_data = True",

test/test_ios.py

@@ -3,6 +3,7 @@ import platform
 import shutil
 import subprocess
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -22,7 +23,7 @@ import platform
 from unittest import TestCase
 
 class TestPlatform(TestCase):
-    def test_platform(self):
+    def test_platform(self) -> None:
         self.assertEqual(platform.machine(), "{platform.machine()}")
 
 """
@@ -59,7 +60,12 @@ def skip_if_ios_testing_not_supported() -> None:
         {"CIBW_PLATFORM": "ios", "CIBW_BUILD_FRONTEND": "build"},
     ],
 )
-def test_ios_platforms(tmp_path, build_config, monkeypatch, capfd):
+def test_ios_platforms(
+    tmp_path: Path,
+    build_config: dict[str, str],
+    monkeypatch: pytest.MonkeyPatch,
+    capfd: pytest.CaptureFixture[str],
+) -> None:
     skip_if_ios_testing_not_supported()
 
     # Create a temporary "bin" directory, symlink a tool that we know eixsts
@@ -67,7 +73,9 @@ def test_ios_platforms(tmp_path, build_config, monkeypatch, capfd):
     # and add the temp bin directory to the PATH.
     tools_dir = tmp_path / "bin"
     tools_dir.mkdir()
-    tools_dir.joinpath("does-exist").symlink_to(shutil.which("true"))
+    true_app = shutil.which("true")
+    assert true_app is not None
+    tools_dir.joinpath("does-exist").symlink_to(true_app)
 
     monkeypatch.setenv("PATH", str(tools_dir), prepend=os.pathsep)
 
@@ -110,7 +118,7 @@ def test_ios_platforms(tmp_path, build_config, monkeypatch, capfd):
 
 
 @pytest.mark.serial
-def test_no_test_sources(tmp_path, capfd):
+def test_no_test_sources(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """Build will provide a helpful error if pytest is run and test-sources is not defined."""
     skip_if_ios_testing_not_supported()
 
@@ -138,7 +146,7 @@ def test_no_test_sources(tmp_path, capfd):
     )
 
 
-def test_ios_testing_with_placeholder(tmp_path, capfd):
+def test_ios_testing_with_placeholder(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """
     Tests with the {project} placeholder are not supported on iOS, because the test command
     is run in the simulator.
@@ -168,7 +176,7 @@ def test_ios_testing_with_placeholder(tmp_path, capfd):
 
 @pytest.mark.serial
 @pytest.mark.flaky(reruns=2)
-def test_ios_test_command_short_circuit(tmp_path, capfd):
+def test_ios_test_command_short_circuit(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     skip_if_ios_testing_not_supported()
 
     project_dir = tmp_path / "project"
@@ -196,7 +204,7 @@ def test_ios_test_command_short_circuit(tmp_path, capfd):
     assert "Zen of Python" not in captured.out + captured.err
 
 
-def test_missing_xbuild_tool(tmp_path, capfd):
+def test_missing_xbuild_tool(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """Build will fail if xbuild-tools references a non-existent tool."""
     skip_if_ios_testing_not_supported()
 
@@ -220,7 +228,7 @@ def test_missing_xbuild_tool(tmp_path, capfd):
     assert "Could not find a 'does-not-exist' executable on the path." in captured.err
 
 
-def test_no_xbuild_tool_definition(tmp_path, capfd):
+def test_no_xbuild_tool_definition(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """Build will succeed with a warning if there is no xbuild-tools definition."""
     skip_if_ios_testing_not_supported()
 
@@ -254,7 +262,7 @@ def test_no_xbuild_tool_definition(tmp_path, capfd):
     assert "Your project configuration does not define any cross-build tools." in captured.err
 
 
-def test_empty_xbuild_tool_definition(tmp_path, capfd):
+def test_empty_xbuild_tool_definition(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """Build will succeed with no warning if there is an empty xbuild-tools definition."""
     skip_if_ios_testing_not_supported()
 
@@ -286,7 +294,9 @@ def test_empty_xbuild_tool_definition(tmp_path, capfd):
 
 
 @pytest.mark.serial
-def test_ios_test_command_without_python_dash_m(tmp_path, capfd):
+def test_ios_test_command_without_python_dash_m(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str]
+) -> None:
     """pytest should be able to run without python -m, but it should warn."""
     skip_if_ios_testing_not_supported()
 
@@ -296,7 +306,7 @@ def test_ios_test_command_without_python_dash_m(tmp_path, capfd):
     project.files["tests/__init__.py"] = ""
     project.files["tests/test_spam.py"] = textwrap.dedent("""
         import spam
-        def test_spam():
+        def test_spam() -> None:
             assert spam.filter("spam") == 0
             assert spam.filter("ham") != 0
     """)
@@ -324,7 +334,7 @@ def test_ios_test_command_without_python_dash_m(tmp_path, capfd):
     assert "iOS tests configured with a test command which doesn't start with 'python -m'" in err
 
 
-def test_ios_test_command_invalid(tmp_path, capfd):
+def test_ios_test_command_invalid(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     """Test command should raise an error if it's clearly invalid."""
     skip_if_ios_testing_not_supported()
 
@@ -347,7 +357,7 @@ def test_ios_test_command_invalid(tmp_path, capfd):
     assert "iOS tests configured with a test command which doesn't start with 'python -m'" in err
 
 
-def test_repair_step(tmp_path):
+def test_repair_step(tmp_path: Path) -> None:
     """Build will succeed & the custom repair step is called."""
     skip_if_ios_testing_not_supported()
 

test/test_linux_python.py

@@ -1,12 +1,13 @@
 import platform
 import subprocess
+from pathlib import Path
 
 import pytest
 
 from . import test_projects, utils
 
 
-def test_python_exist(tmp_path, capfd):
+def test_python_exist(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the test is only relevant to the linux build")
     machine = platform.machine()

test/test_macos_archs.py

@@ -1,4 +1,5 @@
 import platform
+from pathlib import Path
 
 import pytest
 
@@ -19,7 +20,7 @@ ALL_MACOS_WHEELS = {
 DEPLOYMENT_TARGET_TOO_LOW_WARNING = "Bumping MACOSX_DEPLOYMENT_TARGET"
 
 
-def test_cross_compiled_build(tmp_path):
+def test_cross_compiled_build(tmp_path: Path) -> None:
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
     if utils.get_xcode_version() < (12, 2):
@@ -51,7 +52,12 @@ def test_cross_compiled_build(tmp_path):
         },
     ],
 )
-def test_cross_compiled_test(tmp_path, capfd, build_universal2, test_config):
+def test_cross_compiled_test(
+    tmp_path: Path,
+    capfd: pytest.CaptureFixture[str],
+    build_universal2: bool,
+    test_config: dict[str, str],
+) -> None:
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
     if utils.get_xcode_version() < (12, 2):
@@ -110,7 +116,9 @@ def test_cross_compiled_test(tmp_path, capfd, build_universal2, test_config):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_deployment_target_warning_is_firing(tmp_path, capfd):
+def test_deployment_target_warning_is_firing(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str]
+) -> None:
     # force the warning to check that we can detect it if it happens
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
@@ -133,7 +141,9 @@ def test_deployment_target_warning_is_firing(tmp_path, capfd):
 
 
 @pytest.mark.parametrize("skip_arm64_test", [False, True])
-def test_universal2_testing_on_x86_64(tmp_path, capfd, skip_arm64_test):
+def test_universal2_testing_on_x86_64(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str], skip_arm64_test: bool
+) -> None:
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
     if utils.get_xcode_version() < (12, 2):
@@ -172,7 +182,9 @@ def test_universal2_testing_on_x86_64(tmp_path, capfd, skip_arm64_test):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_universal2_testing_on_arm64(build_frontend_env, tmp_path, capfd):
+def test_universal2_testing_on_arm64(
+    build_frontend_env: dict[str, str], tmp_path: Path, capfd: pytest.CaptureFixture[str]
+) -> None:
     # cibuildwheel should test the universal2 wheel on both x86_64 and arm64, when run on arm64
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
@@ -203,7 +215,9 @@ def test_universal2_testing_on_arm64(build_frontend_env, tmp_path, capfd):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_cp38_arm64_testing(tmp_path, capfd, request):
+def test_cp38_arm64_testing(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str], request: pytest.FixtureRequest
+) -> None:
     if utils.get_platform() != "macos":
         pytest.skip("this test is only relevant to macos")
     if utils.get_xcode_version() < (12, 2):
@@ -238,7 +252,9 @@ def test_cp38_arm64_testing(tmp_path, capfd, request):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_cp38_arm64_testing_universal2_installer(tmp_path, capfd, request):
+def test_cp38_arm64_testing_universal2_installer(
+    tmp_path: Path, capfd: pytest.CaptureFixture[str], request: pytest.FixtureRequest
+) -> None:
     if not request.config.getoption("--run-cp38-universal2"):
         pytest.skip("needs --run-cp38-universal2 option to run")
 

test/test_manylinuxXXXX_only.py

@@ -1,5 +1,6 @@
 import platform
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -61,7 +62,7 @@ project_with_manylinux_symbols = test_projects.new_c_project(
     ],
 )
 @pytest.mark.usefixtures("docker_cleanup")
-def test(manylinux_image, tmp_path):
+def test(manylinux_image: str, tmp_path: Path) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the container image test is only relevant to the linux build")
 

test/test_meson_python.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 import packaging.utils
 
 from . import test_projects, utils
@@ -5,7 +7,7 @@ from . import test_projects, utils
 meson_project = test_projects.new_meson_project()
 
 
-def test_meson_python_basic(tmp_path, build_frontend_env):
+def test_meson_python_basic(tmp_path: Path, build_frontend_env: dict[str, str]) -> None:
     """Test that cibuildwheel can build a project with meson-python backend."""
     project_dir = tmp_path / "project"
 

test/test_musllinux_X_Y_only.py

@@ -1,4 +1,5 @@
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -27,7 +28,7 @@ project_with_manylinux_symbols = test_projects.new_c_project(
     ["musllinux_1_2"],
 )
 @pytest.mark.usefixtures("docker_cleanup")
-def test(musllinux_image, tmp_path):
+def test(musllinux_image: str, tmp_path: Path) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("the container image test is only relevant to the linux build")
 

test/test_pep518.py

@@ -1,4 +1,5 @@
 import textwrap
+from pathlib import Path
 
 from . import test_projects, utils
 
@@ -29,7 +30,7 @@ build-backend = "setuptools.build_meta"
 """
 
 
-def test_pep518(tmp_path, build_frontend_env):
+def test_pep518(tmp_path: Path, build_frontend_env: dict[str, str]) -> None:
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 

test/test_pure_wheel.py

@@ -1,4 +1,5 @@
 import subprocess
+from pathlib import Path
 
 import pytest
 
@@ -23,7 +24,7 @@ def a_function():
 """
 
 
-def test(tmp_path, capfd):
+def test(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     # this test checks that if a pure wheel is generated, the build should
     # fail.
     project_dir = tmp_path / "project"

test/test_pyodide.py

@@ -3,6 +3,7 @@ import os
 import subprocess
 import sys
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -48,7 +49,7 @@ if __name__ == "__main__":
 
 
 @pytest.mark.parametrize("use_pyproject_toml", [True, False])
-def test_pyodide_build(tmp_path, use_pyproject_toml):
+def test_pyodide_build(tmp_path: Path, use_pyproject_toml: bool) -> None:
     if sys.platform == "win32":
         pytest.skip("pyodide-build doesn't work correctly on Windows")
 
@@ -88,7 +89,7 @@ def test_pyodide_build(tmp_path, use_pyproject_toml):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_pyodide_version_incompatible(tmp_path, capfd):
+def test_pyodide_version_incompatible(tmp_path: Path, capfd: pytest.CaptureFixture[str]) -> None:
     if sys.platform == "win32":
         pytest.skip("pyodide-build doesn't work correctly on Windows")
 
@@ -110,19 +111,19 @@ def test_pyodide_version_incompatible(tmp_path, capfd):
 
 
 @pytest.mark.parametrize("expect_failure", [True, False])
-def test_pyodide_build_and_test(tmp_path, expect_failure):
+def test_pyodide_build_and_test(tmp_path: Path, expect_failure: bool) -> None:
     if sys.platform == "win32":
         pytest.skip("pyodide-build doesn't work correctly on Windows")
 
     if expect_failure:
         basic_project.files["test/spam_test.py"] = textwrap.dedent(r"""
-            def test_filter():
+            def test_filter() -> None:
                 assert 0 == 1
         """)
     else:
         basic_project.files["test/spam_test.py"] = textwrap.dedent(r"""
             import spam
-            def test_filter():
+            def test_filter() -> None:
                 assert spam.filter("spam") == 0
         """)
     basic_project.generate(tmp_path)
@@ -149,7 +150,7 @@ def test_pyodide_build_and_test(tmp_path, expect_failure):
         assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_pyodide_repair_wheel(tmp_path):
+def test_pyodide_repair_wheel(tmp_path: Path) -> None:
     if sys.platform == "win32":
         pytest.skip("pyodide-build doesn't work correctly on Windows")
 

test/test_ssl.py

@@ -1,4 +1,5 @@
 import textwrap
+from pathlib import Path
 
 import pytest
 
@@ -32,7 +33,7 @@ project_with_ssl_tests = test_projects.new_c_project(
 
 
 @pytest.mark.flaky(reruns=2)
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     # this test checks that SSL is working in the build environment using
     # some checks in setup.py.
     project_dir = tmp_path / "project"

test/test_subdir_package.py

@@ -1,6 +1,7 @@
 from pathlib import Path
 
 import jinja2
+import pytest
 
 from . import utils
 from .test_projects import TestProject
@@ -31,7 +32,7 @@ print('before_build.py executed!')
 """
 
 
-def test(capfd, tmp_path):
+def test(capfd: pytest.CaptureFixture[str], tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     subdir_package_project.generate(project_dir)
 

test/test_testing.py

@@ -43,11 +43,11 @@ def path_contains(parent, child):
 
 
 class TestSpam(TestCase):
-    def test_filter(self):
+    def test_filter(self) -> None:
         self.assertEqual(0, spam.filter("spam"))
         self.assertNotEqual(0, spam.filter("ham"))
 
-    def test_virtualenv(self):
+    def test_virtualenv(self) -> None:
         # sys.prefix is different from sys.base_prefix when running a virtualenv
         # See https://docs.python.org/3/library/venv.html, which virtualenv seems
         # to honor in recent releases
@@ -58,7 +58,7 @@ class TestSpam(TestCase):
         self.assertTrue(path_contains(sys.prefix, spam.__file__))
         self.assertIn("VIRTUAL_ENV", os.environ)
 
-    def test_uname(self):
+    def test_uname(self) -> None:
         if platform.system() == "Windows":
             return
         # if we're running in 32-bit Python, check that the machine is i686.
@@ -69,7 +69,7 @@ class TestSpam(TestCase):
 '''
 
 
-def test(tmp_path):
+def test(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_a_test.generate(project_dir)
 
@@ -90,7 +90,7 @@ def test(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_extras_require(tmp_path):
+def test_extras_require(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_a_test.generate(project_dir)
 
@@ -112,7 +112,7 @@ def test_extras_require(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_dependency_groups(tmp_path):
+def test_dependency_groups(tmp_path: Path) -> None:
     group_project = project_with_a_test.copy()
     group_project.files["pyproject.toml"] = inspect.cleandoc("""
         [build-system]
@@ -149,12 +149,12 @@ project_with_a_failing_test.files["test/spam_test.py"] = r"""
 from unittest import TestCase
 
 class TestSpam(TestCase):
-    def test_something(self):
+    def test_something(self) -> None:
         self.fail('this test is supposed to fail')
 """
 
 
-def test_failing_test(tmp_path):
+def test_failing_test(tmp_path: Path) -> None:
     """Ensure a failing test causes cibuildwheel to error out and exit"""
     project_dir = tmp_path / "project"
     output_dir = tmp_path / "output"
@@ -215,7 +215,7 @@ def test_bare_pytest_invocation(
     )
 
 
-def test_test_sources(tmp_path):
+def test_test_sources(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     project_with_a_test.generate(project_dir)
 
@@ -235,7 +235,7 @@ def test_test_sources(tmp_path):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_test_environment(tmp_path):
+def test_test_environment(tmp_path: Path) -> None:
     project_dir = tmp_path / "project"
     test_projects.new_c_project().generate(project_dir)
 

test/test_troubleshooting.py

@@ -1,4 +1,5 @@
 import subprocess
+from pathlib import Path
 
 import pytest
 
@@ -9,7 +10,12 @@ SO_FILE_WARNING = "NOTE: Shared object (.so) files found in this project."
 
 
 @pytest.mark.parametrize("project_contains_so_files", [False, True])
-def test_failed_build_with_so_files(tmp_path, capfd, build_frontend_env, project_contains_so_files):
+def test_failed_build_with_so_files(
+    tmp_path: Path,
+    capfd: pytest.CaptureFixture[str],
+    build_frontend_env: dict[str, str],
+    project_contains_so_files: bool,
+) -> None:
     project = TestProject()
     project.files["setup.py"] = "raise Exception('this build will fail')\n"
     if project_contains_so_files:
@@ -35,7 +41,11 @@ def test_failed_build_with_so_files(tmp_path, capfd, build_frontend_env, project
 
 
 @pytest.mark.parametrize("project_contains_so_files", [False, True])
-def test_failed_repair_with_so_files(tmp_path, capfd, project_contains_so_files):
+def test_failed_repair_with_so_files(
+    tmp_path: Path,
+    capfd: pytest.CaptureFixture[str],
+    project_contains_so_files: bool,
+) -> None:
     if utils.get_platform() != "linux":
         pytest.skip("this test is only relevant to the linux build")
 

test/test_wheel_tag.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 import pytest
 
 from . import test_projects, utils
@@ -5,7 +7,7 @@ from . import test_projects, utils
 basic_project = test_projects.new_c_project()
 
 
-def test_wheel_tag_is_correct_when_using_macosx_deployment_target(tmp_path):
+def test_wheel_tag_is_correct_when_using_macosx_deployment_target(tmp_path: Path) -> None:
     if utils.get_platform() != "macos":
         pytest.skip("This test is only relevant to MACOSX_DEPLOYMENT_TARGET")
 

test/test_windows.py

@@ -38,7 +38,9 @@ def skip_if_no_msvc(arm64: bool = False) -> None:
 
 
 @pytest.mark.parametrize("use_pyproject_toml", [True, False])
-def test_wheel_tag_is_correct_when_using_windows_cross_compile(tmp_path, use_pyproject_toml):
+def test_wheel_tag_is_correct_when_using_windows_cross_compile(
+    tmp_path: Path, use_pyproject_toml: bool
+) -> None:
     if utils.get_platform() != "windows":
         pytest.skip("This test is only relevant to Windows")
 

test/utils.py

@@ -11,7 +11,7 @@ import sys
 from collections.abc import Generator, Mapping, Sequence
 from pathlib import Path
 from tempfile import TemporaryDirectory
-from typing import Any, Final
+from typing import Final
 
 import pytest
 
@@ -458,7 +458,7 @@ def get_xcode_version() -> tuple[int, int]:
     return (int(version_parts[0]), int(version_parts[1]))
 
 
-def skip_if_pyodide(reason: str) -> Any:
+def skip_if_pyodide(reason: str) -> pytest.MarkDecorator:
     return pytest.mark.skipif(get_platform() == "pyodide", reason=reason)
 
 

unit_test/architecture_test.py

@@ -6,6 +6,7 @@ import pytest
 
 import cibuildwheel.architecture
 from cibuildwheel.architecture import Architecture, arch_synonym
+from cibuildwheel.typing import PlatformName
 
 
 @pytest.fixture(
@@ -20,7 +21,9 @@ from cibuildwheel.architecture import Architecture, arch_synonym
         pytest.param(("windows", "win32", "ARM64", "arm"), id="windows-arm"),
     ]
 )
-def platform_machine(request, monkeypatch):
+def platform_machine(
+    request: pytest.FixtureRequest, monkeypatch: pytest.MonkeyPatch
+) -> tuple[str, str]:
     platform_name, platform_value, machine_value, machine_name = request.param
     monkeypatch.setattr(sys, "platform", platform_value)
     monkeypatch.setattr(platform_module, "machine", lambda: machine_value)
@@ -28,7 +31,7 @@ def platform_machine(request, monkeypatch):
     return platform_name, machine_name
 
 
-def test_arch_auto(platform_machine):
+def test_arch_auto(platform_machine: tuple[str, str]) -> None:
     _, machine_name = platform_machine
 
     arch_set = Architecture.auto_archs("linux")
@@ -52,7 +55,7 @@ def test_arch_auto(platform_machine):
     assert arch_set == expected[machine_name]
 
 
-def test_arch_auto64(platform_machine):
+def test_arch_auto64(platform_machine: tuple[str, str]) -> None:
     _, machine_name = platform_machine
 
     arch_set = Architecture.parse_config("auto64", "linux")
@@ -68,7 +71,7 @@ def test_arch_auto64(platform_machine):
     assert arch_set == expected[machine_name]
 
 
-def test_arch_auto32(platform_machine):
+def test_arch_auto32(platform_machine: tuple[str, str]) -> None:
     _, machine_name = platform_machine
 
     arch_set = Architecture.parse_config("auto32", "linux")
@@ -83,7 +86,7 @@ def test_arch_auto32(platform_machine):
     assert arch_set == expected[machine_name]
 
 
-def test_arch_auto_no_aarch32(monkeypatch):
+def test_arch_auto_no_aarch32(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(sys, "platform", "linux")
     monkeypatch.setattr(platform_module, "machine", lambda: "aarch64")
     monkeypatch.setattr(shutil, "which", lambda *args, **kwargs: None)
@@ -103,14 +106,14 @@ def test_arch_auto_no_aarch32(monkeypatch):
     assert arch_set == set()
 
 
-def test_arch_native_on_ios(monkeypatch):
+def test_arch_native_on_ios(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(sys, "platform", "darwin")
     monkeypatch.setattr(platform_module, "machine", lambda: "arm64")
     arch_set = Architecture.parse_config("native", platform="ios")
     assert arch_set == {Architecture.arm64_iphonesimulator}
 
 
-def test_arch_auto_on_ios(monkeypatch):
+def test_arch_auto_on_ios(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(sys, "platform", "darwin")
     monkeypatch.setattr(platform_module, "machine", lambda: "arm64")
     arch_set = Architecture.parse_config("auto", platform="ios")
@@ -130,5 +133,7 @@ def test_arch_auto_on_ios(monkeypatch):
         ("x86", "windows", "macos", None),
     ],
 )
-def test_arch_synonym(arch, from_platform, to_platform, expected):
+def test_arch_synonym(
+    arch: str, from_platform: PlatformName, to_platform: PlatformName, expected: str | None
+) -> None:
     assert arch_synonym(arch, from_platform, to_platform) == expected

unit_test/build_ids_test.py

@@ -6,7 +6,7 @@ from cibuildwheel.extra import Printable, dump_python_configurations
 from cibuildwheel.util import resources
 
 
-def test_compare_configs():
+def test_compare_configs() -> None:
     txt = resources.BUILD_PLATFORMS.read_text()
 
     with resources.BUILD_PLATFORMS.open("rb") as f2:
@@ -18,7 +18,7 @@ def test_compare_configs():
     assert new_txt == txt
 
 
-def test_dump_with_Version():
+def test_dump_with_Version() -> None:
     # MyPy doesn't understand deeply nested dicts correctly
     example: dict[str, dict[str, list[dict[str, Printable]]]] = {
         "windows": {

unit_test/build_selector_test.py

@@ -4,7 +4,7 @@ import cibuildwheel.selector
 from cibuildwheel.selector import BuildSelector, EnableGroup
 
 
-def test_build():
+def test_build() -> None:
     build_selector = BuildSelector(
         build_config="cp3*-* *-manylinux*", skip_config="", enable=frozenset([EnableGroup.PyPy])
     )
@@ -41,7 +41,7 @@ def test_build():
     assert not build_selector("pp311-win_amd64")
 
 
-def test_build_filter_pre():
+def test_build_filter_pre() -> None:
     build_selector = BuildSelector(
         build_config="cp3*-* *-manylinux*",
         skip_config="",
@@ -55,7 +55,7 @@ def test_build_filter_pre():
     assert not build_selector("cp313t-manylinux_x86_64")
 
 
-def test_build_filter_pypy():
+def test_build_filter_pypy() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -67,7 +67,7 @@ def test_build_filter_pypy():
     assert not build_selector("pp39-manylinux_x86_64")
 
 
-def test_build_filter_pypy_eol():
+def test_build_filter_pypy_eol() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -79,7 +79,7 @@ def test_build_filter_pypy_eol():
     assert build_selector("pp39-manylinux_x86_64")
 
 
-def test_build_filter_pypy_all():
+def test_build_filter_pypy_all() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -91,7 +91,7 @@ def test_build_filter_pypy_all():
     assert build_selector("pp39-manylinux_x86_64")
 
 
-def test_build_filter_pyodide_prerelease():
+def test_build_filter_pyodide_prerelease() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -101,7 +101,7 @@ def test_build_filter_pyodide_prerelease():
     assert build_selector("cp313-pyodide_wasm32")
 
 
-def test_build_filter_pyodide():
+def test_build_filter_pyodide() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -111,7 +111,7 @@ def test_build_filter_pyodide():
     assert build_selector("cp313-pyodide_wasm32")
 
 
-def test_skip():
+def test_skip() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="pp310-* cp3?-manylinux_i686 cp36-win* *-win32",
@@ -136,7 +136,7 @@ def test_skip():
     assert build_selector("cp37-win_amd64")
 
 
-def test_build_and_skip():
+def test_build_and_skip() -> None:
     build_selector = BuildSelector(
         build_config="cp36-* cp37-macosx* *-manylinux*",
         skip_config="pp37-* cp37-manylinux_i686",
@@ -160,7 +160,7 @@ def test_build_and_skip():
     assert not build_selector("cp37-win_amd64")
 
 
-def test_build_braces():
+def test_build_braces() -> None:
     build_selector = BuildSelector(build_config="cp{36,37}*", skip_config="")
 
     assert build_selector("cp36-manylinux_x86_64")
@@ -169,7 +169,7 @@ def test_build_braces():
     assert not build_selector("cp39-manylinux_x86_64")
 
 
-def test_build_limited_python():
+def test_build_limited_python() -> None:
     build_selector = BuildSelector(
         build_config="*",
         skip_config="",
@@ -190,7 +190,7 @@ def test_build_limited_python():
     assert build_selector("gp311_242-win_amd64")
 
 
-def test_build_limited_python_partial():
+def test_build_limited_python_partial() -> None:
     build_selector = BuildSelector(
         build_config="*", skip_config="", requires_python=SpecifierSet(">=3.6, !=3.7.*")
     )
@@ -201,7 +201,7 @@ def test_build_limited_python_partial():
     assert build_selector("cp39-manylinux_x86_64")
 
 
-def test_build_limited_python_patch():
+def test_build_limited_python_patch() -> None:
     build_selector = BuildSelector(
         build_config="*", skip_config="", requires_python=SpecifierSet(">=3.6.8")
     )
@@ -210,13 +210,13 @@ def test_build_limited_python_patch():
     assert build_selector("cp37-manylinux_x86_64")
 
 
-def test_build_free_threaded_python():
+def test_build_free_threaded_python() -> None:
     build_selector = BuildSelector(build_config="*", skip_config="", enable=frozenset(EnableGroup))
 
     assert build_selector("cp313t-manylinux_x86_64")
 
 
-def test_testing_selector():
+def test_testing_selector() -> None:
     # This is not a global import to keep pytest from collecting it as a test
     test_selector = cibuildwheel.selector.TestSelector(skip_config="cp36-*")
 

unit_test/conftest.py

@@ -6,7 +6,7 @@ import pytest
 MOCK_PACKAGE_DIR = Path("some_package_dir")
 
 
-def pytest_addoption(parser):
+def pytest_addoption(parser: pytest.Parser) -> None:
     parser.addoption("--run-docker", action="store_true", default=False, help="run docker tests")
     parser.addoption("--run-podman", action="store_true", default=False, help="run podman tests")
     parser.addoption(
@@ -18,13 +18,13 @@ def pytest_addoption(parser):
 
 
 @pytest.fixture
-def fake_package_dir(tmp_path, monkeypatch):
+def fake_package_dir(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> list[str]:
     """
     Monkey-patch enough for the main() function to run
     """
     real_path_exists = Path.exists
 
-    def mock_path_exists(path):
+    def mock_path_exists(path: Path) -> bool:
         if str(path).endswith(str(MOCK_PACKAGE_DIR / "setup.py")):
             return True
         else:

unit_test/download_test.py

@@ -1,4 +1,5 @@
 import ssl
+from pathlib import Path
 
 import certifi
 import pytest
@@ -8,21 +9,21 @@ from cibuildwheel.util.file import download
 DOWNLOAD_URL = "https://cdn.jsdelivr.net/gh/pypa/cibuildwheel@v1.6.3/requirements-dev.txt"
 
 
-def test_download(monkeypatch, tmp_path):
+def test_download(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
     monkeypatch.delenv("SSL_CERT_FILE", raising=False)
     dest = tmp_path / "file.txt"
     download(DOWNLOAD_URL, dest)
     assert len(dest.read_bytes()) == 134
 
 
-def test_download_good_ssl_cert_file(monkeypatch, tmp_path):
+def test_download_good_ssl_cert_file(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
     monkeypatch.setenv("SSL_CERT_FILE", certifi.where())
     dest = tmp_path / "file.txt"
     download(DOWNLOAD_URL, dest)
     assert len(dest.read_bytes()) == 134
 
 
-def test_download_bad_ssl_cert_file(monkeypatch, tmp_path):
+def test_download_bad_ssl_cert_file(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
     bad_cafile = tmp_path / "ca.pem"
     bad_cafile.write_text("bad certificates")
     monkeypatch.setenv("SSL_CERT_FILE", str(bad_cafile))

unit_test/environment_test.py

@@ -7,7 +7,7 @@ from cibuildwheel.environment import parse_environment
 PYTHON_ECHO = f"'{sys.executable}' -c \"import sys; print(*sys.argv[1:])\""
 
 
-def test_basic_parsing():
+def test_basic_parsing() -> None:
     environment_recipe = parse_environment("VAR=1 VBR=2")
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={})
@@ -15,7 +15,7 @@ def test_basic_parsing():
     assert environment_dict == {"VAR": "1", "VBR": "2"}
 
 
-def test_quotes():
+def test_quotes() -> None:
     environment_recipe = parse_environment("A=1 VAR=\"1 NOT_A_VAR=2\" VBR='vbr'")
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={})
@@ -23,7 +23,7 @@ def test_quotes():
     assert environment_dict == {"A": "1", "VAR": "1 NOT_A_VAR=2", "VBR": "vbr"}
 
 
-def test_inheritance():
+def test_inheritance() -> None:
     environment_recipe = parse_environment("PATH=$PATH:/usr/local/bin")
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={"PATH": "/usr/bin"})
@@ -31,7 +31,7 @@ def test_inheritance():
     assert environment_dict == {"PATH": "/usr/bin:/usr/local/bin"}
 
 
-def test_shell_eval():
+def test_shell_eval() -> None:
     environment_recipe = parse_environment(f'VAR="$({PYTHON_ECHO} "a   test" string)"')
 
     env_copy = os.environ.copy()
@@ -42,7 +42,7 @@ def test_shell_eval():
     assert environment_dict["VAR"] == "a   test string"
 
 
-def test_shell_eval_and_env():
+def test_shell_eval_and_env() -> None:
     environment_recipe = parse_environment(f'VAR="$({PYTHON_ECHO} "$PREV_VAR" string)"')
 
     prev_environment = {**os.environ, "PREV_VAR": "1 2 3"}
@@ -51,7 +51,7 @@ def test_shell_eval_and_env():
     assert environment_dict == {**prev_environment, "VAR": "1 2 3 string"}
 
 
-def test_empty_var():
+def test_empty_var() -> None:
     environment_recipe = parse_environment("CFLAGS=")
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={"CFLAGS": "-Wall"})
@@ -59,7 +59,7 @@ def test_empty_var():
     assert environment_dict == {"CFLAGS": ""}
 
 
-def test_no_vars():
+def test_no_vars() -> None:
     environment_recipe = parse_environment("")
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={})
@@ -67,7 +67,7 @@ def test_no_vars():
     assert environment_dict == {}
 
 
-def test_no_vars_pass_through():
+def test_no_vars_pass_through() -> None:
     environment_recipe = parse_environment("")
 
     environment_dict = environment_recipe.as_dictionary(
@@ -77,7 +77,7 @@ def test_no_vars_pass_through():
     assert environment_dict == {"CIBUILDWHEEL": "awesome"}
 
 
-def test_operators_inside_eval():
+def test_operators_inside_eval() -> None:
     environment_recipe = parse_environment(
         f'SOMETHING="$({PYTHON_ECHO} a; {PYTHON_ECHO} b; {PYTHON_ECHO} c)"'
     )
@@ -88,7 +88,7 @@ def test_operators_inside_eval():
     assert environment_dict.get("SOMETHING") == "a\nb\nc"
 
 
-def test_substitution_with_backslash():
+def test_substitution_with_backslash() -> None:
     environment_recipe = parse_environment('PATH2="somewhere_else;$PATH1"')
 
     environment_dict = environment_recipe.as_dictionary(prev_environment={"PATH1": "c:\\folder\\"})
@@ -96,7 +96,7 @@ def test_substitution_with_backslash():
     assert environment_dict.get("PATH2") == "somewhere_else;c:\\folder\\"
 
 
-def test_awkwardly_quoted_variable():
+def test_awkwardly_quoted_variable() -> None:
     environment_recipe = parse_environment(
         f'VAR2=something"like this""$VAR1"$VAR1$({PYTHON_ECHO} "there is more")"$({PYTHON_ECHO} "and more!")"'
     )

unit_test/main_commands_test.py

@@ -1,6 +1,7 @@
 import errno
 import shutil
 import sys
+from pathlib import Path
 
 import pytest
 
@@ -8,7 +9,9 @@ import cibuildwheel.__main__ as main_module
 from cibuildwheel.__main__ import main
 
 
-def test_clean_cache_when_cache_exists(tmp_path, monkeypatch, capfd):
+def test_clean_cache_when_cache_exists(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str]
+) -> None:
     fake_cache_dir = (tmp_path / "cibw_cache").resolve()
     monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
 
@@ -40,7 +43,9 @@ def test_clean_cache_when_cache_exists(tmp_path, monkeypatch, capfd):
     assert not fake_cache_dir.exists()
 
 
-def test_clean_cache_when_cache_does_not_exist(tmp_path, monkeypatch, capfd):
+def test_clean_cache_when_cache_does_not_exist(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str]
+) -> None:
     fake_cache_dir = (tmp_path / "nonexistent_cache").resolve()
     monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
 
@@ -55,7 +60,9 @@ def test_clean_cache_when_cache_does_not_exist(tmp_path, monkeypatch, capfd):
     assert f"Cache directory does not exist: {fake_cache_dir}" in out
 
 
-def test_clean_cache_with_error(tmp_path, monkeypatch, capfd):
+def test_clean_cache_with_error(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str]
+) -> None:
     fake_cache_dir = (tmp_path / "cibw_cache").resolve()
     monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
 
@@ -73,7 +80,7 @@ def test_clean_cache_with_error(tmp_path, monkeypatch, capfd):
 
     monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
 
-    def fake_rmtree(path):  # noqa: ARG001
+    def fake_rmtree(path: Path) -> None:  # noqa: ARG001
         raise OSError(errno.EACCES, "Permission denied")
 
     monkeypatch.setattr(shutil, "rmtree", fake_rmtree)
@@ -88,7 +95,9 @@ def test_clean_cache_with_error(tmp_path, monkeypatch, capfd):
     assert "Error clearing cache:" in err
 
 
-def test_clean_cache_without_sentinel(tmp_path, monkeypatch, capfd):
+def test_clean_cache_without_sentinel(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str]
+) -> None:
     fake_cache_dir = (tmp_path / "not_a_cache").resolve()
     monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
 
@@ -106,7 +115,9 @@ def test_clean_cache_without_sentinel(tmp_path, monkeypatch, capfd):
     assert fake_cache_dir.exists()
 
 
-def test_clean_cache_with_invalid_signature(tmp_path, monkeypatch, capfd):
+def test_clean_cache_with_invalid_signature(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capfd: pytest.CaptureFixture[str]
+) -> None:
     fake_cache_dir = (tmp_path / "fake_cache").resolve()
     monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
 

unit_test/main_tests/conftest.py

@@ -2,7 +2,9 @@ import contextlib
 import platform as platform_module
 import subprocess
 import sys
+from collections.abc import Generator, Iterator
 from pathlib import Path
+from typing import Any
 
 import pytest
 
@@ -15,27 +17,27 @@ from cibuildwheel.util import file
 class ArgsInterceptor:
     def __init__(self) -> None:
         self.call_count = 0
-        self.args: tuple[object, ...] | None = None
-        self.kwargs: dict[str, object] | None = None
+        self.args: tuple[Any, ...] = ()
+        self.kwargs: dict[str, Any] = {}
 
-    def __call__(self, *args: object, **kwargs: object) -> None:
+    def __call__(self, *args: Any, **kwargs: Any) -> None:
         self.call_count += 1
         self.args = args
         self.kwargs = kwargs
 
 
 @pytest.fixture(autouse=True)
-def mock_protection(monkeypatch):
+def mock_protection(monkeypatch: pytest.MonkeyPatch) -> None:
     """
     Ensure that a unit test will never actually run a cibuildwheel 'build'
     function, which shouldn't be run on a developer's machine
     """
 
-    def fail_on_call(*args, **kwargs):
+    def fail_on_call(*args: object, **kwargs: object) -> None:
         msg = "This should never be called"
         raise RuntimeError(msg)
 
-    def ignore_call(*args, **kwargs):
+    def ignore_call(*args: object, **kwargs: object) -> None:
         pass
 
     monkeypatch.setattr(subprocess, "Popen", fail_on_call)
@@ -49,27 +51,27 @@ def mock_protection(monkeypatch):
 
 
 @pytest.fixture(autouse=True)
-def fake_package_dir_autouse(fake_package_dir):
+def fake_package_dir_autouse(fake_package_dir: list[str]) -> None:
     pass
 
 
 @pytest.fixture(autouse=True)
-def disable_print_wheels(monkeypatch):
+def disable_print_wheels(monkeypatch: pytest.MonkeyPatch) -> None:
     @contextlib.contextmanager
-    def empty_cm(*args, **kwargs):
+    def empty_cm(*args: object, **kwargs: object) -> Generator[None, None, None]:
         yield
 
     monkeypatch.setattr(Logger, "print_summary", empty_cm)
 
 
 @pytest.fixture
-def allow_empty(monkeypatch, fake_package_dir):
+def allow_empty(monkeypatch: pytest.MonkeyPatch, fake_package_dir: list[str]) -> None:
     monkeypatch.setattr(sys, "argv", [*fake_package_dir, "--allow-empty"])
 
 
 @pytest.fixture(params=["linux", "macos", "windows"])
-def platform(request, monkeypatch):
-    platform_value = request.param
+def platform(request: pytest.FixtureRequest, monkeypatch: pytest.MonkeyPatch) -> str:
+    platform_value: str = request.param
     monkeypatch.setenv("CIBW_PLATFORM", platform_value)
 
     if platform_value == "windows":
@@ -84,7 +86,7 @@ def platform(request, monkeypatch):
 
 
 @pytest.fixture
-def intercepted_build_args(monkeypatch):
+def intercepted_build_args(monkeypatch: pytest.MonkeyPatch) -> Iterator[ArgsInterceptor]:
     intercepted = ArgsInterceptor()
 
     monkeypatch.setattr(android, "build", intercepted)

unit_test/main_tests/main_options_test.py

@@ -1,7 +1,9 @@
 import sys
 import tomllib
+from collections.abc import Mapping
 from fnmatch import fnmatch
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 import pytest
 
@@ -13,10 +15,15 @@ from cibuildwheel.selector import BuildSelector, EnableGroup
 from cibuildwheel.util import resources
 from cibuildwheel.util.packaging import DependencyConstraints
 
+if TYPE_CHECKING:
+    from .conftest import ArgsInterceptor
+
 # CIBW_PLATFORM is tested in main_platform_test.py
 
 
-def test_old_free_threaded(monkeypatch, capsys):
+def test_old_free_threaded(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setenv("CIBW_FREE_THREADED_SUPPORT", "ON")
 
     with pytest.raises(SystemExit):
@@ -29,7 +36,9 @@ def test_old_free_threaded(monkeypatch, capsys):
 
 
 @pytest.mark.usefixtures("platform")
-def test_output_dir(intercepted_build_args, monkeypatch):
+def test_output_dir(
+    intercepted_build_args: "ArgsInterceptor", monkeypatch: pytest.MonkeyPatch
+) -> None:
     OUTPUT_DIR = Path("some_output_dir")
 
     monkeypatch.setenv("CIBW_OUTPUT_DIR", str(OUTPUT_DIR))
@@ -40,7 +49,7 @@ def test_output_dir(intercepted_build_args, monkeypatch):
 
 
 @pytest.mark.usefixtures("platform")
-def test_output_dir_default(intercepted_build_args):
+def test_output_dir_default(intercepted_build_args: "ArgsInterceptor") -> None:
     main()
 
     assert intercepted_build_args.args[0].globals.output_dir == Path("wheelhouse").resolve()
@@ -48,7 +57,11 @@ def test_output_dir_default(intercepted_build_args):
 
 @pytest.mark.usefixtures("platform")
 @pytest.mark.parametrize("also_set_environment", [False, True])
-def test_output_dir_argument(also_set_environment, intercepted_build_args, monkeypatch):
+def test_output_dir_argument(
+    also_set_environment: bool,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     OUTPUT_DIR = Path("some_output_dir")
 
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--output-dir", str(OUTPUT_DIR)])
@@ -61,7 +74,9 @@ def test_output_dir_argument(also_set_environment, intercepted_build_args, monke
 
 
 @pytest.mark.usefixtures("platform", "allow_empty")
-def test_build_selector(intercepted_build_args, monkeypatch):
+def test_build_selector(
+    intercepted_build_args: "ArgsInterceptor", monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_BUILD", "cp313-*")
     monkeypatch.setenv("CIBW_SKIP", "cp39-*")
 
@@ -76,7 +91,9 @@ def test_build_selector(intercepted_build_args, monkeypatch):
 
 
 @pytest.mark.usefixtures("platform", "allow_empty")
-def test_invalid_build_selector(monkeypatch, capsys):
+def test_invalid_build_selector(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setenv("CIBW_BUILD", "invalid")
 
     with pytest.raises(SystemExit) as e:
@@ -95,7 +112,12 @@ def test_invalid_build_selector(monkeypatch, capsys):
     ],
 )
 @pytest.mark.usefixtures("platform", "intercepted_build_args")
-def test_invalid_skip_selector(monkeypatch, capsys, option_name, option_env_var):
+def test_invalid_skip_selector(
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+    option_name: str,
+    option_env_var: str,
+) -> None:
     monkeypatch.setenv(option_env_var, "invalid")
 
     main()
@@ -109,7 +131,9 @@ def test_invalid_skip_selector(monkeypatch, capsys, option_name, option_env_var)
     "selector", ["*-macosx_universal2:arm64", "*-macosx_universal2:x86_64", "*-macosx_arm64"]
 )
 @pytest.mark.usefixtures("platform", "intercepted_build_args")
-def test_valid_test_skip_selector(monkeypatch, capsys, selector):
+def test_valid_test_skip_selector(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str], selector: str
+) -> None:
     monkeypatch.setenv("CIBW_TEST_SKIP", selector)
 
     main()
@@ -121,7 +145,9 @@ def test_valid_test_skip_selector(monkeypatch, capsys, selector):
 
 @pytest.mark.parametrize("selector", ["*-macosx_universal2:invalid", "*-macosx_arm64:arm64"])
 @pytest.mark.usefixtures("platform", "intercepted_build_args")
-def test_invalid_test_skip_selector(monkeypatch, capsys, selector):
+def test_invalid_test_skip_selector(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str], selector: str
+) -> None:
     monkeypatch.setenv("CIBW_TEST_SKIP", selector)
 
     main()
@@ -132,7 +158,7 @@ def test_invalid_test_skip_selector(monkeypatch, capsys, selector):
 
 
 @pytest.mark.usefixtures("platform", "intercepted_build_args")
-def test_empty_selector(monkeypatch):
+def test_empty_selector(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("CIBW_SKIP", "*")
 
     with pytest.raises(SystemExit) as e:
@@ -161,8 +187,13 @@ def test_empty_selector(monkeypatch):
     ],
 )
 def test_manylinux_images(
-    architecture, image, full_image, platform, intercepted_build_args, monkeypatch
-):
+    architecture: str,
+    image: str | None,
+    full_image: str,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if image is not None:
         monkeypatch.setenv("CIBW_MANYLINUX_" + architecture.upper() + "_IMAGE", image)
 
@@ -194,8 +225,12 @@ def get_default_repair_command(platform: str) -> str:
 @pytest.mark.parametrize("repair_command", [None, "repair", "repair -w {dest_dir} {wheel}"])
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_repair_command(
-    repair_command, platform_specific, platform, intercepted_build_args, monkeypatch
-):
+    repair_command: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if repair_command is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_REPAIR_WHEEL_COMMAND_" + platform.upper(), repair_command)
@@ -216,7 +251,13 @@ def test_repair_command(
     [{}, {"something": "value"}, {"something": "value", "something_else": "other_value"}],
 )
 @pytest.mark.parametrize("platform_specific", [False, True])
-def test_environment(environment, platform_specific, platform, intercepted_build_args, monkeypatch):
+def test_environment(
+    environment: Mapping[str, str],
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     env_string = " ".join(f"{k}={v}" for k, v in environment.items())
     if platform_specific:
         monkeypatch.setenv("CIBW_ENVIRONMENT_" + platform.upper(), env_string)
@@ -236,8 +277,12 @@ def test_environment(environment, platform_specific, platform, intercepted_build
 @pytest.mark.parametrize("test_requires", [None, "requirement other_requirement"])
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_test_requires(
-    test_requires, platform_specific, platform, intercepted_build_args, monkeypatch
-):
+    test_requires: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if test_requires is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_TEST_REQUIRES_" + platform.upper(), test_requires)
@@ -254,7 +299,13 @@ def test_test_requires(
 
 @pytest.mark.parametrize("test_extras", [None, "extras"])
 @pytest.mark.parametrize("platform_specific", [False, True])
-def test_test_extras(test_extras, platform_specific, platform, intercepted_build_args, monkeypatch):
+def test_test_extras(
+    test_extras: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if test_extras is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_TEST_EXTRAS_" + platform.upper(), test_extras)
@@ -272,8 +323,12 @@ def test_test_extras(test_extras, platform_specific, platform, intercepted_build
 @pytest.mark.parametrize("test_command", [None, "test --command"])
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_test_command(
-    test_command, platform_specific, platform, intercepted_build_args, monkeypatch
-):
+    test_command: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if test_command is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_TEST_COMMAND_" + platform.upper(), test_command)
@@ -291,8 +346,12 @@ def test_test_command(
 @pytest.mark.parametrize("before_build", [None, "before --build"])
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_before_build(
-    before_build, platform_specific, platform, intercepted_build_args, monkeypatch
-):
+    before_build: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if before_build is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_BEFORE_BUILD_" + platform.upper(), before_build)
@@ -309,8 +368,12 @@ def test_before_build(
 @pytest.mark.parametrize("build_verbosity", [None, 0, 2, -2, 4, -4])
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_build_verbosity(
-    build_verbosity, platform_specific, platform, intercepted_build_args, monkeypatch
-):
+    build_verbosity: int | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if build_verbosity is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_BUILD_VERBOSITY_" + platform.upper(), str(build_verbosity))
@@ -326,7 +389,12 @@ def test_build_verbosity(
 
 
 @pytest.mark.parametrize("platform_specific", [False, True])
-def test_config_settings(platform_specific, platform, intercepted_build_args, monkeypatch):
+def test_config_settings(
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     config_settings = (
         'setting=value setting=value2 triplet=1 triplet=2 triplet=3 other="something else"'
     )
@@ -376,7 +444,9 @@ def test_config_settings(platform_specific, platform, intercepted_build_args, mo
     ],
 )
 @pytest.mark.usefixtures("platform", "intercepted_build_args", "allow_empty")
-def test_build_selector_deprecated_error(monkeypatch, selector, pattern, capsys):
+def test_build_selector_deprecated_error(
+    monkeypatch: pytest.MonkeyPatch, selector: str, pattern: str, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setenv(selector, pattern)
     monkeypatch.delenv("CIBW_ENABLE", raising=False)
 
@@ -396,7 +466,13 @@ def test_build_selector_deprecated_error(monkeypatch, selector, pattern, capsys)
 
 @pytest.mark.parametrize("before_all", ["", None, "test text"])
 @pytest.mark.parametrize("platform_specific", [False, True])
-def test_before_all(before_all, platform_specific, platform, intercepted_build_args, monkeypatch):
+def test_before_all(
+    before_all: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     if before_all is not None:
         if platform_specific:
             monkeypatch.setenv("CIBW_BEFORE_ALL_" + platform.upper(), before_all)
@@ -417,8 +493,13 @@ def test_before_all(before_all, platform_specific, platform, intercepted_build_a
 )
 @pytest.mark.parametrize("platform_specific", [False, True])
 def test_dependency_versions(
-    dependency_versions, platform_specific, platform, intercepted_build_args, monkeypatch, tmp_path
-):
+    dependency_versions: str | None,
+    platform_specific: bool,
+    platform: str,
+    intercepted_build_args: "ArgsInterceptor",
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
     option_value = dependency_versions
 
     if dependency_versions == "FILE":
@@ -443,13 +524,16 @@ def test_dependency_versions(
         assert dependency_constraints == DependencyConstraints.latest()
     elif dependency_versions == "FILE":
         assert dependency_constraints.base_file_path
+        assert option_value is not None
         assert dependency_constraints.base_file_path.samefile(Path(option_value))
     elif dependency_versions.startswith("packages:"):
         assert dependency_constraints.packages == ["pip==21.0.0"]
 
 
 @pytest.mark.parametrize("method", ["unset", "command_line", "env_var"])
-def test_debug_traceback(monkeypatch, method, capfd):
+def test_debug_traceback(
+    monkeypatch: pytest.MonkeyPatch, method: str, capfd: pytest.CaptureFixture[str]
+) -> None:
     if method == "command_line":
         monkeypatch.setattr(sys, "argv", [*sys.argv, "--debug-traceback"])
     elif method == "env_var":
@@ -471,7 +555,9 @@ def test_debug_traceback(monkeypatch, method, capfd):
 
 
 @pytest.mark.parametrize("method", ["unset", "command_line", "env_var"])
-def test_enable(method, intercepted_build_args, monkeypatch):
+def test_enable(
+    method: str, intercepted_build_args: "ArgsInterceptor", monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.delenv("CIBW_ENABLE", raising=False)
 
     if method == "command_line":
@@ -489,7 +575,9 @@ def test_enable(method, intercepted_build_args, monkeypatch):
         assert enable_groups == frozenset([EnableGroup.PyPy, EnableGroup.GraalPy])
 
 
-def test_enable_all(intercepted_build_args, monkeypatch):
+def test_enable_all(
+    intercepted_build_args: "ArgsInterceptor", monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--enable", "all"])
 
     main()
@@ -498,7 +586,9 @@ def test_enable_all(intercepted_build_args, monkeypatch):
     assert enable_groups == EnableGroup.all_groups()
 
 
-def test_enable_arg_inherits(intercepted_build_args, monkeypatch):
+def test_enable_arg_inherits(
+    intercepted_build_args: "ArgsInterceptor", monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ENABLE", "pypy graalpy")
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--enable", "cpython-prerelease"])
 
@@ -511,7 +601,9 @@ def test_enable_arg_inherits(intercepted_build_args, monkeypatch):
     )
 
 
-def test_enable_arg_error_message(monkeypatch, capsys):
+def test_enable_arg_error_message(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--enable", "invalid_group"])
 
     with pytest.raises(SystemExit) as ex:
@@ -522,7 +614,7 @@ def test_enable_arg_error_message(monkeypatch, capsys):
     assert "Valid group names are:" in err
 
 
-def test_defaults(platform, intercepted_build_args):
+def test_defaults(platform: str, intercepted_build_args: "ArgsInterceptor") -> None:
     main()
 
     build_options: BuildOptions = intercepted_build_args.args[0].build_options(identifier=None)

unit_test/main_tests/main_platform_test.py

@@ -5,12 +5,18 @@ import pytest
 from cibuildwheel.__main__ import main
 from cibuildwheel.architecture import Architecture
 from cibuildwheel.selector import EnableGroup
+from cibuildwheel.typing import PlatformName
 
 from ..conftest import MOCK_PACKAGE_DIR
+from .conftest import ArgsInterceptor
 
 
 @pytest.mark.parametrize("option_value", [None, "auto", ""])
-def test_platform_unset_or_auto(monkeypatch, intercepted_build_args, option_value):
+def test_platform_unset_or_auto(
+    monkeypatch: pytest.MonkeyPatch,
+    intercepted_build_args: ArgsInterceptor,
+    option_value: str | None,
+) -> None:
     if option_value is None:
         monkeypatch.delenv("CIBW_PLATFORM", raising=False)
     else:
@@ -31,7 +37,9 @@ def test_platform_unset_or_auto(monkeypatch, intercepted_build_args, option_valu
         pytest.fail(f"Unknown platform: {sys.platform}")
 
 
-def test_unknown_platform_on_ci(monkeypatch, capsys):
+def test_unknown_platform_on_ci(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setenv("CI", "true")
     monkeypatch.setattr(sys, "platform", "nonexistent")
     monkeypatch.delenv("CIBW_PLATFORM", raising=False)
@@ -44,7 +52,9 @@ def test_unknown_platform_on_ci(monkeypatch, capsys):
     assert 'Unable to detect platform from "sys.platform"' in err
 
 
-def test_unknown_platform(monkeypatch, capsys):
+def test_unknown_platform(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setenv("CIBW_PLATFORM", "nonexistent")
 
     with pytest.raises(SystemExit) as exit:
@@ -55,7 +65,9 @@ def test_unknown_platform(monkeypatch, capsys):
     assert "Unsupported platform: nonexistent" in err
 
 
-def test_platform_argument(platform, intercepted_build_args, monkeypatch):
+def test_platform_argument(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_PLATFORM", "nonexistent")
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--platform", platform])
 
@@ -67,14 +79,14 @@ def test_platform_argument(platform, intercepted_build_args, monkeypatch):
 
 
 @pytest.mark.usefixtures("platform")
-def test_platform_environment(intercepted_build_args):
+def test_platform_environment(intercepted_build_args: ArgsInterceptor) -> None:
     main()
     options = intercepted_build_args.args[0]
 
     assert options.globals.package_dir == MOCK_PACKAGE_DIR.resolve()
 
 
-def test_archs_default(platform, intercepted_build_args):
+def test_archs_default(platform: str, intercepted_build_args: ArgsInterceptor) -> None:
     main()
     options = intercepted_build_args.args[0]
 
@@ -87,7 +99,12 @@ def test_archs_default(platform, intercepted_build_args):
 
 
 @pytest.mark.parametrize("use_env_var", [False, True])
-def test_archs_argument(platform, intercepted_build_args, monkeypatch, use_env_var):
+def test_archs_argument(
+    platform: str,
+    intercepted_build_args: ArgsInterceptor,
+    monkeypatch: pytest.MonkeyPatch,
+    use_env_var: bool,
+) -> None:
     if use_env_var:
         monkeypatch.setenv("CIBW_ARCHS", "ppc64le")
     else:
@@ -105,7 +122,9 @@ def test_archs_argument(platform, intercepted_build_args, monkeypatch, use_env_v
         assert options.globals.architectures == {Architecture.ppc64le}
 
 
-def test_archs_platform_specific(platform, intercepted_build_args, monkeypatch):
+def test_archs_platform_specific(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "unused")
     monkeypatch.setenv("CIBW_ARCHS_LINUX", "ppc64le")
     monkeypatch.setenv("CIBW_ARCHS_WINDOWS", "x86")
@@ -122,7 +141,9 @@ def test_archs_platform_specific(platform, intercepted_build_args, monkeypatch):
         assert options.globals.architectures == {Architecture.x86_64}
 
 
-def test_archs_platform_native(platform, intercepted_build_args, monkeypatch):
+def test_archs_platform_native(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "native")
 
     main()
@@ -134,7 +155,9 @@ def test_archs_platform_native(platform, intercepted_build_args, monkeypatch):
         assert options.globals.architectures == {Architecture.AMD64}
 
 
-def test_archs_platform_auto64(platform, intercepted_build_args, monkeypatch):
+def test_archs_platform_auto64(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "auto64")
 
     main()
@@ -146,7 +169,9 @@ def test_archs_platform_auto64(platform, intercepted_build_args, monkeypatch):
         assert options.globals.architectures == {Architecture.AMD64}
 
 
-def test_archs_platform_auto32(platform, intercepted_build_args, monkeypatch):
+def test_archs_platform_auto32(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "auto32")
 
     if platform == "macos":
@@ -165,7 +190,9 @@ def test_archs_platform_auto32(platform, intercepted_build_args, monkeypatch):
             assert options.globals.architectures == {Architecture.x86}
 
 
-def test_archs_platform_all(platform, intercepted_build_args, monkeypatch):
+def test_archs_platform_all(
+    platform: str, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "all")
 
     main()
@@ -204,7 +231,12 @@ def test_archs_platform_all(platform, intercepted_build_args, monkeypatch):
         ("cp311-macosx_x86_64", "macos"),
     ),
 )
-def test_only_argument(intercepted_build_args, monkeypatch, only, plat):
+def test_only_argument(
+    intercepted_build_args: ArgsInterceptor,
+    monkeypatch: pytest.MonkeyPatch,
+    only: str,
+    plat: PlatformName,
+) -> None:
     monkeypatch.setenv("CIBW_BUILD", "unused")
     monkeypatch.setenv("CIBW_SKIP", "unused")
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--only", only])
@@ -220,14 +252,14 @@ def test_only_argument(intercepted_build_args, monkeypatch, only, plat):
 
 
 @pytest.mark.parametrize("only", ("cp311-manylxinux_x86_64", "some_linux_thing"))
-def test_only_failed(monkeypatch, only):
+def test_only_failed(monkeypatch: pytest.MonkeyPatch, only: str) -> None:
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--only", only])
 
     with pytest.raises(SystemExit):
         main()
 
 
-def test_only_no_platform(monkeypatch):
+def test_only_no_platform(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(
         sys, "argv", [*sys.argv, "--only", "cp311-manylinux_x86_64", "--platform", "macos"]
     )
@@ -236,7 +268,7 @@ def test_only_no_platform(monkeypatch):
         main()
 
 
-def test_only_no_archs(monkeypatch):
+def test_only_no_archs(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(
         sys, "argv", [*sys.argv, "--only", "cp311-manylinux_x86_64", "--archs", "x86_64"]
     )
@@ -254,7 +286,12 @@ def test_only_no_archs(monkeypatch):
         ("CIBW_PLATFORM", "macos"),
     ),
 )
-def test_only_overrides_env_vars(monkeypatch, intercepted_build_args, envvar_name, envvar_value):
+def test_only_overrides_env_vars(
+    monkeypatch: pytest.MonkeyPatch,
+    intercepted_build_args: ArgsInterceptor,
+    envvar_name: str,
+    envvar_value: str,
+) -> None:
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--only", "cp311-manylinux_x86_64"])
     monkeypatch.setenv(envvar_name, envvar_value)
 
@@ -267,7 +304,9 @@ def test_only_overrides_env_vars(monkeypatch, intercepted_build_args, envvar_nam
     assert options.globals.architectures == Architecture.all_archs("linux")
 
 
-def test_pyodide_on_windows(monkeypatch, capsys):
+def test_pyodide_on_windows(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
     monkeypatch.setattr(sys, "platform", "win32")
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--only", "cp312-pyodide_wasm32"])
 
@@ -280,7 +319,9 @@ def test_pyodide_on_windows(monkeypatch, capsys):
     assert "Building for pyodide is not supported on Windows" in err
 
 
-def test_empty_archs_platform(platform, intercepted_build_args, monkeypatch):
+def test_empty_archs_platform(
+    platform: PlatformName, intercepted_build_args: ArgsInterceptor, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBW_ARCHS", "")
 
     main()

unit_test/main_tests/main_requires_python_test.py

@@ -1,14 +1,17 @@
 import sys
 import textwrap
+from pathlib import Path
 
 import pytest
 from packaging.specifiers import SpecifierSet
 
 from cibuildwheel.__main__ import main
 
+from .conftest import ArgsInterceptor
+
 
 @pytest.fixture(autouse=True)
-def fake_package_dir(monkeypatch, tmp_path):
+def fake_package_dir(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> Path:
     """
     Set up a fake project
     """
@@ -24,7 +27,7 @@ def fake_package_dir(monkeypatch, tmp_path):
 
 
 @pytest.mark.usefixtures("platform")
-def test_no_override(intercepted_build_args):
+def test_no_override(intercepted_build_args: ArgsInterceptor) -> None:
     main()
 
     options = intercepted_build_args.args[0]
@@ -37,7 +40,9 @@ def test_no_override(intercepted_build_args):
 
 
 @pytest.mark.usefixtures("platform")
-def test_override_env(monkeypatch, intercepted_build_args):
+def test_override_env(
+    monkeypatch: pytest.MonkeyPatch, intercepted_build_args: ArgsInterceptor
+) -> None:
     monkeypatch.setenv("CIBW_PROJECT_REQUIRES_PYTHON", ">=3.8")
 
     main()
@@ -52,7 +57,9 @@ def test_override_env(monkeypatch, intercepted_build_args):
 
 
 @pytest.mark.usefixtures("platform")
-def test_override_setup_cfg(intercepted_build_args, fake_package_dir):
+def test_override_setup_cfg(
+    intercepted_build_args: ArgsInterceptor, fake_package_dir: Path
+) -> None:
     fake_package_dir.joinpath("setup.cfg").write_text(
         textwrap.dedent(
             """
@@ -74,7 +81,9 @@ def test_override_setup_cfg(intercepted_build_args, fake_package_dir):
 
 
 @pytest.mark.usefixtures("platform")
-def test_override_pyproject_toml(intercepted_build_args, fake_package_dir):
+def test_override_pyproject_toml(
+    intercepted_build_args: ArgsInterceptor, fake_package_dir: Path
+) -> None:
     fake_package_dir.joinpath("pyproject.toml").write_text(
         textwrap.dedent(
             """
@@ -96,7 +105,9 @@ def test_override_pyproject_toml(intercepted_build_args, fake_package_dir):
 
 
 @pytest.mark.usefixtures("platform")
-def test_override_setup_py_simple(intercepted_build_args, fake_package_dir):
+def test_override_setup_py_simple(
+    intercepted_build_args: ArgsInterceptor, fake_package_dir: Path
+) -> None:
     fake_package_dir.joinpath("setup.py").write_text(
         textwrap.dedent(
             """

unit_test/oci_container_test.py

@@ -1,3 +1,4 @@
+import contextlib
 import json
 import os
 import random
@@ -6,6 +7,7 @@ import subprocess
 import sys
 import textwrap
 import time
+from collections.abc import Iterator
 from contextlib import nullcontext
 from pathlib import Path, PurePath, PurePosixPath
 
@@ -34,7 +36,7 @@ PODMAN = OCIContainerEngineConfig(name="podman")
 
 
 @pytest.fixture(params=["docker", "podman"], scope="module")
-def container_engine(request):
+def container_engine(request: pytest.FixtureRequest) -> Iterator[OCIContainerEngineConfig]:
     if request.param == "docker" and not request.config.getoption("--run-docker"):
         pytest.skip("need --run-docker option to run")
     if request.param == "podman" and not request.config.getoption("--run-podman"):
@@ -63,21 +65,21 @@ def container_engine(request):
 # Tests
 
 
-def test_simple(container_engine):
+def test_simple(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=DEFAULT_OCI_PLATFORM
     ) as container:
         assert container.call(["echo", "hello"], capture_output=True) == "hello\n"
 
 
-def test_no_lf(container_engine):
+def test_no_lf(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=DEFAULT_OCI_PLATFORM
     ) as container:
         assert container.call(["printf", "hello"], capture_output=True) == "hello"
 
 
-def test_debug_info(container_engine):
+def test_debug_info(container_engine: OCIContainerEngineConfig) -> None:
     container = OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=DEFAULT_OCI_PLATFORM
     )
@@ -86,7 +88,7 @@ def test_debug_info(container_engine):
         pass
 
 
-def test_environment(container_engine):
+def test_environment(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=DEFAULT_OCI_PLATFORM
     ) as container:
@@ -98,7 +100,9 @@ def test_environment(container_engine):
         )
 
 
-def test_environment_pass(container_engine, monkeypatch):
+def test_environment_pass(
+    container_engine: OCIContainerEngineConfig, monkeypatch: pytest.MonkeyPatch
+) -> None:
     monkeypatch.setenv("CIBUILDWHEEL", "1")
     monkeypatch.setenv("SOURCE_DATE_EPOCH", "1489957071")
     with OCIContainer(
@@ -111,7 +115,7 @@ def test_environment_pass(container_engine, monkeypatch):
         )
 
 
-def test_cwd(container_engine):
+def test_cwd(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine,
         image=DEFAULT_IMAGE,
@@ -122,7 +126,7 @@ def test_cwd(container_engine):
         assert container.call(["pwd"], capture_output=True, cwd="/opt") == "/opt\n"
 
 
-def test_container_removed(container_engine):
+def test_container_removed(container_engine: OCIContainerEngineConfig) -> None:
     # test is flaky on some platforms, implement retry for 5 second
     timeout = 50  # * 100 ms = 5s
     with OCIContainer(
@@ -157,7 +161,7 @@ def test_container_removed(container_engine):
     assert container_name not in docker_containers_listing
 
 
-def test_large_environment(container_engine):
+def test_large_environment(container_engine: OCIContainerEngineConfig) -> None:
     # max environment variable size is 128kB
     long_env_var_length = 127 * 1024
     large_environment = {
@@ -177,7 +181,7 @@ def test_large_environment(container_engine):
         )
 
 
-def test_binary_output(container_engine):
+def test_binary_output(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=DEFAULT_OCI_PLATFORM
     ) as container:
@@ -472,7 +476,9 @@ def test_create_args_volume(tmp_path: Path, container_engine: OCIContainerEngine
         ),
     ],
 )
-def test_parse_engine_config(config, name, create_args, capsys):
+def test_parse_engine_config(
+    config: str, name: str, create_args: tuple[str, ...], capsys: pytest.CaptureFixture[str]
+) -> None:
     engine_config = OCIContainerEngineConfig.from_config_string(config)
     assert engine_config.name == name
     assert engine_config.create_args == create_args
@@ -485,7 +491,7 @@ def test_parse_engine_config(config, name, create_args, capsys):
 
 
 @pytest.mark.skipif(DEFAULT_OCI_PLATFORM != OCIPlatform.AMD64, reason="Only runs on x86_64")
-def test_enforce_32_bit(container_engine):
+def test_enforce_32_bit(container_engine: OCIContainerEngineConfig) -> None:
     with OCIContainer(
         engine=container_engine, image=DEFAULT_IMAGE, oci_platform=OCIPlatform.i386
     ) as container:
@@ -567,7 +573,7 @@ def test_local_image(
 
 
 @pytest.mark.parametrize("platform", list(OCIPlatform))
-def test_multiarch_image(container_engine, platform):
+def test_multiarch_image(container_engine: OCIContainerEngineConfig, platform: OCIPlatform) -> None:
     if detect_ci_provider() == CIProvider.travis_ci and DEFAULT_OCI_PLATFORM not in {
         OCIPlatform.AMD64,
         platform,
@@ -657,8 +663,13 @@ def test_multiarch_image(container_engine, platform):
         ("podman", '{"Client":{"Version":"2.1.0~rc1"}}', pytest.raises(OCIEngineTooOldError)),
     ],
 )
-def test_engine_version(engine_name, version, context, monkeypatch):
-    def mockcall(*args, **kwargs):
+def test_engine_version(
+    engine_name: str,
+    version: str | None,
+    context: contextlib.AbstractContextManager[None],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    def mockcall(*args: object, **kwargs: object) -> str:
         if version is None:
             raise subprocess.CalledProcessError(1, " ".join(str(arg) for arg in args))
         return version

unit_test/option_prepare_test.py

@@ -3,7 +3,7 @@ import subprocess
 import sys
 import typing
 from contextlib import contextmanager
-from pathlib import PurePosixPath
+from pathlib import Path, PurePosixPath
 from unittest import mock
 
 import pytest
@@ -18,19 +18,19 @@ ALL_IDS = DEFAULT_IDS | {"cp313t", "pp38", "pp39", "pp310", "pp311", "gp311_242"
 
 
 @pytest.fixture
-def mock_build_container(monkeypatch):
-    def fail_on_call(*args, **kwargs):
+def mock_build_container(monkeypatch: pytest.MonkeyPatch) -> None:
+    def fail_on_call(*args: object, **kwargs: object) -> None:
         msg = "This should never be called"
         raise RuntimeError(msg)
 
-    def ignore_call(*args, **kwargs):
+    def ignore_call(*args: object, **kwargs: object) -> None:
         pass
 
     @contextmanager
-    def nullcontext(enter_result=None):
+    def nullcontext(enter_result: object = None) -> typing.Generator[object, None, None]:
         yield enter_result
 
-    def ignore_context_call(*args, **kwargs):
+    def ignore_context_call(*args: object, **kwargs: object) -> typing.ContextManager[object]:
         return nullcontext(kwargs)
 
     monkeypatch.setenv("CIBW_PLATFORM", "linux")
@@ -49,7 +49,7 @@ def mock_build_container(monkeypatch):
 
 
 @pytest.mark.usefixtures("mock_build_container", "fake_package_dir")
-def test_build_default_launches(monkeypatch):
+def test_build_default_launches(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--platform=linux"])
     monkeypatch.setenv("CIBW_ARCHS", "auto64 auto32")
     monkeypatch.delenv("CIBW_ENABLE", raising=False)
@@ -95,7 +95,7 @@ def test_build_default_launches(monkeypatch):
 
 
 @pytest.mark.usefixtures("mock_build_container")
-def test_build_with_override_launches(monkeypatch, tmp_path):
+def test_build_with_override_launches(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
     pkg_dir = tmp_path / "cibw_package"
     pkg_dir.mkdir()
 

unit_test/options_test.py

@@ -48,7 +48,7 @@ manylinux-x86_64-image = "manylinux_2_34"
 """
 
 
-def test_options_1(tmp_path, monkeypatch):
+def test_options_1(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     with tmp_path.joinpath("pyproject.toml").open("w") as f:
         f.write(PYPROJECT_1)
 
@@ -96,7 +96,7 @@ def test_options_1(tmp_path, monkeypatch):
     assert local.pyodide_version == "0.28.0"
 
 
-def test_passthrough(tmp_path, monkeypatch):
+def test_passthrough(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     with tmp_path.joinpath("pyproject.toml").open("w") as f:
         f.write(PYPROJECT_1)
 
@@ -126,7 +126,9 @@ def test_passthrough(tmp_path, monkeypatch):
         "a trailing backslash \\",
     ],
 )
-def test_passthrough_evil(tmp_path, monkeypatch, env_var_value):
+def test_passthrough_evil(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, env_var_value: str
+) -> None:
     args = CommandLineArguments.defaults()
     args.package_dir = tmp_path
 
@@ -157,7 +159,7 @@ xfail_env_parse = pytest.mark.xfail(
         pytest.param("a trailing backslash \\", marks=[xfail_env_parse]),
     ],
 )
-def test_toml_environment_evil(tmp_path, env_var_value):
+def test_toml_environment_evil(tmp_path: Path, env_var_value: str) -> None:
     args = CommandLineArguments.defaults()
     args.package_dir = tmp_path
 
@@ -296,7 +298,7 @@ def test_container_engine_option(
     assert parsed_container_engine.disable_host_mount == result_disable_host_mount
 
 
-def test_environment_pass_references():
+def test_environment_pass_references() -> None:
     options = Options(
         platform="linux",
         command_line_arguments=CommandLineArguments.defaults(),

unit_test/options_toml_test.py

@@ -1,5 +1,6 @@
 import shlex
-from typing import TYPE_CHECKING
+from pathlib import Path
+from typing import Any, cast
 
 import pytest
 
@@ -12,9 +13,7 @@ from cibuildwheel.options import (
     ShlexTableFormat,
     _resolve_cascade,
 )
-
-if TYPE_CHECKING:
-    from pathlib import Path
+from cibuildwheel.typing import PlatformName
 
 PYPROJECT_1 = """
 [tool.cibuildwheel]
@@ -39,12 +38,12 @@ test-requires = ["other", "many"]
 
 
 @pytest.fixture(params=["linux", "macos", "windows"])
-def platform(request):
-    return request.param
+def platform(request: pytest.FixtureRequest) -> PlatformName:
+    return cast("PlatformName", request.param)
 
 
 @pytest.mark.parametrize("fname", ["pyproject.toml", "cibuildwheel.toml"])
-def test_simple_settings(tmp_path, platform, fname):
+def test_simple_settings(tmp_path: Path, platform: PlatformName, fname: str) -> None:
     config_file_path: Path = tmp_path / fname
     config_file_path.write_text(PYPROJECT_1)
 
@@ -83,7 +82,7 @@ def test_simple_settings(tmp_path, platform, fname):
         options_reader.get("test-extras", option_format=ShlexTableFormat())
 
 
-def test_envvar_override(tmp_path, platform):
+def test_envvar_override(tmp_path: Path, platform: PlatformName) -> None:
     config_file_path: Path = tmp_path / "pyproject.toml"
     config_file_path.write_text(PYPROJECT_1)
 
@@ -128,7 +127,7 @@ def test_envvar_override(tmp_path, platform):
     assert options_reader.get("test-command") == "mytest"
 
 
-def test_project_global_override_default_platform(tmp_path, platform):
+def test_project_global_override_default_platform(tmp_path: Path, platform: PlatformName) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -140,14 +139,14 @@ repair-wheel-command = "repair-project-global"
     assert options_reader.get("repair-wheel-command") == "repair-project-global"
 
 
-def test_env_global_override_default_platform(platform):
+def test_env_global_override_default_platform(platform: PlatformName) -> None:
     options_reader = OptionsReader(
         platform=platform, env={"CIBW_REPAIR_WHEEL_COMMAND": "repair-env-global"}
     )
     assert options_reader.get("repair-wheel-command") == "repair-env-global"
 
 
-def test_env_global_override_project_platform(tmp_path, platform):
+def test_env_global_override_project_platform(tmp_path: Path, platform: PlatformName) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -161,7 +160,7 @@ repair-wheel-command = "repair-project-macos"
     )
     options_reader = OptionsReader(
         pyproject_toml,
-        platform=platform,
+        platform=cast("Any", platform),
         env={
             "CIBW_REPAIR_WHEEL_COMMAND": "repair-env-global",
         },
@@ -169,7 +168,7 @@ repair-wheel-command = "repair-project-macos"
     assert options_reader.get("repair-wheel-command") == "repair-env-global"
 
 
-def test_global_platform_order(tmp_path, platform):
+def test_global_platform_order(tmp_path: Path, platform: str) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -183,11 +182,11 @@ repair-wheel-command = "repair-project-macos"
 repair-wheel-command = "repair-project-global"
 """
     )
-    options_reader = OptionsReader(pyproject_toml, platform=platform, env={})
+    options_reader = OptionsReader(pyproject_toml, platform=cast("Any", platform), env={})
     assert options_reader.get("repair-wheel-command") == f"repair-project-{platform}"
 
 
-def test_unexpected_key(tmp_path):
+def test_unexpected_key(tmp_path: Path) -> None:
     # Note that platform contents are only checked when running
     # for that platform.
     pyproject_toml = tmp_path / "pyproject.toml"
@@ -204,7 +203,7 @@ repairs-wheel-command = "repair-project-linux"
     assert "repair-wheel-command" in str(excinfo.value)
 
 
-def test_underscores_in_key(tmp_path):
+def test_underscores_in_key(tmp_path: Path) -> None:
     # Note that platform contents are only checked when running
     # for that platform.
     pyproject_toml = tmp_path / "pyproject.toml"
@@ -221,7 +220,7 @@ repair_wheel_command = "repair-project-linux"
     assert "repair-wheel-command" in str(excinfo.value)
 
 
-def test_unexpected_table(tmp_path):
+def test_unexpected_table(tmp_path: Path) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -233,7 +232,7 @@ repair-wheel-command = "repair-project-linux"
         OptionsReader(pyproject_toml, platform="linux", env={})
 
 
-def test_unsupported_join(tmp_path):
+def test_unsupported_join(tmp_path: Path) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -248,7 +247,7 @@ build = ["1", "2"]
         options_reader.get("build")
 
 
-def test_disallowed_a(tmp_path):
+def test_disallowed_a(tmp_path: Path) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -262,7 +261,7 @@ manylinux-x86_64-image = "manylinux1"
         OptionsReader(pyproject_toml, platform="windows", disallow=disallow, env={})
 
 
-def test_environment_override_empty(tmp_path):
+def test_environment_override_empty(tmp_path: Path) -> None:
     pyproject_toml = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """
@@ -296,7 +295,7 @@ manylinux-x86_64-image = ""
 
 
 @pytest.mark.parametrize("ignore_empty", [True, False], ids=["ignore_empty", "no_ignore_empty"])
-def test_resolve_cascade(ignore_empty):
+def test_resolve_cascade(ignore_empty: bool) -> None:
     answer = _resolve_cascade(
         ("not", InheritRule.NONE),
         (None, InheritRule.NONE),
@@ -327,7 +326,7 @@ def test_resolve_cascade(ignore_empty):
 
 @pytest.mark.parametrize("ignore_empty", [True, False], ids=["ignore_empty", "no_ignore_empty"])
 @pytest.mark.parametrize("rule", [InheritRule.PREPEND, InheritRule.NONE, InheritRule.APPEND])
-def test_resolve_cascade_merge_list(ignore_empty, rule):
+def test_resolve_cascade_merge_list(ignore_empty: bool, rule: InheritRule) -> None:
     answer = _resolve_cascade(
         (["a1", "a2"], InheritRule.NONE),
         ([], InheritRule.NONE),
@@ -348,7 +347,7 @@ def test_resolve_cascade_merge_list(ignore_empty, rule):
 
 
 @pytest.mark.parametrize("rule", [InheritRule.PREPEND, InheritRule.NONE, InheritRule.APPEND])
-def test_resolve_cascade_merge_dict(rule):
+def test_resolve_cascade_merge_dict(rule: InheritRule) -> None:
     answer = _resolve_cascade(
         ({"value": "a1", "base": "b1"}, InheritRule.NONE),
         (None, InheritRule.NONE),
@@ -365,7 +364,7 @@ def test_resolve_cascade_merge_dict(rule):
         assert answer == "value=override base=b1"
 
 
-def test_resolve_cascade_merge_strings():
+def test_resolve_cascade_merge_strings() -> None:
     answer = _resolve_cascade(
         ("value=a1 base=b1", InheritRule.NONE),
         ("value=override", InheritRule.APPEND),
@@ -374,7 +373,7 @@ def test_resolve_cascade_merge_strings():
     assert answer == "value=override base=b1"
 
 
-def test_resolve_cascade_merge_different_types():
+def test_resolve_cascade_merge_different_types() -> None:
     answer = _resolve_cascade(
         ("value=a1 base=b1", InheritRule.NONE),
         ({"value": "override"}, InheritRule.APPEND),
@@ -420,11 +419,13 @@ test-command = ["extra-prepend"]
 """
 
 
-def test_pyproject_2(tmp_path, platform):
+def test_pyproject_2(tmp_path: Path, platform: str) -> None:
     pyproject_toml: Path = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(PYPROJECT_2)
 
-    options_reader = OptionsReader(config_file_path=pyproject_toml, platform=platform, env={})
+    options_reader = OptionsReader(
+        config_file_path=pyproject_toml, platform=cast("Any", platform), env={}
+    )
     assert options_reader.get("test-command", option_format=ListFormat(" && ")) == "pyproject"
 
     with options_reader.identifier("random"):
@@ -451,7 +452,7 @@ def test_pyproject_2(tmp_path, platform):
         )
 
 
-def test_overrides_not_a_list(tmp_path, platform):
+def test_overrides_not_a_list(tmp_path: Path, platform: str) -> None:
     pyproject_toml: Path = tmp_path / "pyproject.toml"
 
     pyproject_toml.write_text(
@@ -465,10 +466,10 @@ test-command = "pyproject-override"
     )
 
     with pytest.raises(OptionsReaderError):
-        OptionsReader(config_file_path=pyproject_toml, platform=platform, env={})
+        OptionsReader(config_file_path=pyproject_toml, platform=cast("Any", platform), env={})
 
 
-def test_config_settings(tmp_path):
+def test_config_settings(tmp_path: Path) -> None:
     pyproject_toml: Path = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """\
@@ -485,7 +486,7 @@ other = ["two", "three"]
     )
 
 
-def test_pip_config_settings(tmp_path):
+def test_pip_config_settings(tmp_path: Path) -> None:
     pyproject_toml: Path = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """\
@@ -501,7 +502,7 @@ def test_pip_config_settings(tmp_path):
     )
 
 
-def test_overrides_inherit(tmp_path):
+def test_overrides_inherit(tmp_path: Path) -> None:
     pyproject_toml: Path = tmp_path / "pyproject.toml"
     pyproject_toml.write_text(
         """\

unit_test/projectfiles_test.py

@@ -1,4 +1,5 @@
 import tomllib
+from pathlib import Path
 from textwrap import dedent
 
 import pytest
@@ -10,7 +11,7 @@ from cibuildwheel.projectfiles import (
 )
 
 
-def test_read_setup_py_simple(tmp_path):
+def test_read_setup_py_simple(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -31,7 +32,7 @@ def test_read_setup_py_simple(tmp_path):
     assert get_requires_python_str(tmp_path, {}) == "1.23"
 
 
-def test_read_setup_py_if_main(tmp_path):
+def test_read_setup_py_if_main(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -53,7 +54,7 @@ def test_read_setup_py_if_main(tmp_path):
     assert get_requires_python_str(tmp_path, {}) == "1.23"
 
 
-def test_read_setup_py_if_main_reversed(tmp_path):
+def test_read_setup_py_if_main_reversed(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -75,7 +76,7 @@ def test_read_setup_py_if_main_reversed(tmp_path):
     assert get_requires_python_str(tmp_path, {}) == "1.23"
 
 
-def test_read_setup_py_if_invalid(tmp_path):
+def test_read_setup_py_if_invalid(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -97,7 +98,7 @@ def test_read_setup_py_if_invalid(tmp_path):
     assert not get_requires_python_str(tmp_path, {})
 
 
-def test_read_setup_py_full(tmp_path):
+def test_read_setup_py_full(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w", encoding="utf8") as f:
         f.write(
             dedent(
@@ -123,7 +124,7 @@ def test_read_setup_py_full(tmp_path):
     assert get_requires_python_str(tmp_path, {}) == "1.24"
 
 
-def test_read_setup_py_assign(tmp_path):
+def test_read_setup_py_assign(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -146,7 +147,7 @@ def test_read_setup_py_assign(tmp_path):
     assert get_requires_python_str(tmp_path, {}) is None
 
 
-def test_read_setup_py_None(tmp_path):
+def test_read_setup_py_None(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -169,7 +170,7 @@ def test_read_setup_py_None(tmp_path):
     assert get_requires_python_str(tmp_path, {}) is None
 
 
-def test_read_setup_py_empty(tmp_path):
+def test_read_setup_py_empty(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f:
         f.write(
             dedent(
@@ -191,7 +192,7 @@ def test_read_setup_py_empty(tmp_path):
     assert get_requires_python_str(tmp_path, {}) is None
 
 
-def test_read_setup_cfg(tmp_path):
+def test_read_setup_cfg(tmp_path: Path) -> None:
     with open(tmp_path / "setup.cfg", "w") as f:
         f.write(
             dedent(
@@ -207,7 +208,7 @@ def test_read_setup_cfg(tmp_path):
     assert get_requires_python_str(tmp_path, {}) == "1.234"
 
 
-def test_read_setup_cfg_empty(tmp_path):
+def test_read_setup_cfg_empty(tmp_path: Path) -> None:
     with open(tmp_path / "setup.cfg", "w") as f:
         f.write(
             dedent(
@@ -223,7 +224,7 @@ def test_read_setup_cfg_empty(tmp_path):
     assert get_requires_python_str(tmp_path, {}) is None
 
 
-def test_read_pyproject_toml(tmp_path):
+def test_read_pyproject_toml(tmp_path: Path) -> None:
     with open(tmp_path / "pyproject.toml", "w") as f:
         f.write(
             dedent(
@@ -242,7 +243,7 @@ def test_read_pyproject_toml(tmp_path):
     assert get_requires_python_str(tmp_path, pyproject_toml) == "1.654"
 
 
-def test_read_pyproject_toml_empty(tmp_path):
+def test_read_pyproject_toml_empty(tmp_path: Path) -> None:
     with open(tmp_path / "pyproject.toml", "w") as f:
         f.write(
             dedent(
@@ -258,7 +259,7 @@ def test_read_pyproject_toml_empty(tmp_path):
     assert get_requires_python_str(tmp_path, pyproject_toml) is None
 
 
-def test_read_dep_groups():
+def test_read_dep_groups() -> None:
     pyproject_toml = {"dependency-groups": {"group1": ["pkg1", "pkg2"], "group2": ["pkg3"]}}
     assert resolve_dependency_groups(pyproject_toml) == ()
     assert resolve_dependency_groups(pyproject_toml, "group1") == ("pkg1", "pkg2")
@@ -266,11 +267,11 @@ def test_read_dep_groups():
     assert resolve_dependency_groups(pyproject_toml, "group1", "group2") == ("pkg1", "pkg2", "pkg3")
 
 
-def test_dep_group_no_file_error():
+def test_dep_group_no_file_error() -> None:
     with pytest.raises(FileNotFoundError, match=r"pyproject\.toml"):
         resolve_dependency_groups(None, "test")
 
 
-def test_dep_group_no_section_error():
+def test_dep_group_no_section_error() -> None:
     with pytest.raises(KeyError, match=r"pyproject\.toml"):
         resolve_dependency_groups({}, "test")

unit_test/utils_test.py

@@ -1,5 +1,5 @@
 import textwrap
-from pathlib import PurePath
+from pathlib import Path, PurePath
 from unittest.mock import Mock, call
 
 import pytest
@@ -18,7 +18,7 @@ from cibuildwheel.util.helpers import (
 from cibuildwheel.util.packaging import find_compatible_wheel
 
 
-def test_format_safe():
+def test_format_safe() -> None:
     assert format_safe("{wheel}", wheel="filename.whl") == "filename.whl"
     assert format_safe("command #{wheel}", wheel="filename.whl") == "command {wheel}"
     assert format_safe("{command #{wheel}}", wheel="filename.whl") == "{command {wheel}}"
@@ -37,7 +37,7 @@ def test_format_safe():
     assert format_safe("#{not_a_param} {param}", param="1") == "#{not_a_param} 1"
 
 
-def test_prepare_command():
+def test_prepare_command() -> None:
     assert prepare_command("python -m {project}", project="project") == "python -m project"
     assert prepare_command("python -m {something}", project="project") == "python -m {something}"
     assert (
@@ -103,7 +103,7 @@ def test_find_compatible_wheel_not_found(wheel: str, identifier: str) -> None:
     assert find_compatible_wheel([PurePath(wheel)], identifier) is None
 
 
-def test_fix_ansi_codes_for_github_actions():
+def test_fix_ansi_codes_for_github_actions() -> None:
     input = textwrap.dedent(
         """
         This line is normal
@@ -131,7 +131,7 @@ def test_fix_ansi_codes_for_github_actions():
     assert output == expected
 
 
-def test_parse_key_value_string():
+def test_parse_key_value_string() -> None:
     assert parse_key_value_string("bar", positional_arg_names=["foo"]) == {"foo": ["bar"]}
     assert parse_key_value_string("foo:bar", kw_arg_names=["foo"]) == {"foo": ["bar"]}
     with pytest.raises(ValueError, match="Too many positional arguments"):
@@ -212,7 +212,7 @@ def test_parse_key_value_string():
     }
 
 
-def test_flexible_version_comparisons():
+def test_flexible_version_comparisons() -> None:
     assert FlexibleVersion("2.0") == FlexibleVersion("2")
     assert FlexibleVersion("2.0") < FlexibleVersion("2.1")
     assert FlexibleVersion("2.1") > FlexibleVersion("2")
@@ -227,7 +227,7 @@ def test_flexible_version_comparisons():
 
 
 @pytest.fixture
-def sample_project(tmp_path):
+def sample_project(tmp_path: Path) -> Path:
     """Create a directory structure that contains a range of files."""
     project_path = tmp_path / "project"
 
@@ -324,7 +324,13 @@ def sample_project(tmp_path):
         ),
     ],
 )
-def test_copy_test_sources(tmp_path, sample_project, test_sources, expected, not_expected):
+def test_copy_test_sources(
+    tmp_path: Path,
+    sample_project: Path,
+    test_sources: list[str],
+    expected: list[str],
+    not_expected: list[str],
+) -> None:
     """Test sources can be copied into the test directory."""
     target = tmp_path / "somewhere/test_cwd"
     copy_test_sources(test_sources, sample_project, target)
@@ -336,7 +342,7 @@ def test_copy_test_sources(tmp_path, sample_project, test_sources, expected, not
         assert not (tmp_path / "somewhere/test_cwd" / path).exists()
 
 
-def test_copy_test_sources_missing_file(tmp_path, sample_project):
+def test_copy_test_sources_missing_file(tmp_path: Path, sample_project: Path) -> None:
     """If test_sources references a folder that doesn't exist, an error is raised."""
 
     with pytest.raises(
@@ -350,7 +356,7 @@ def test_copy_test_sources_missing_file(tmp_path, sample_project):
         )
 
 
-def test_copy_test_sources_alternate_copy_into(sample_project):
+def test_copy_test_sources_alternate_copy_into(sample_project: Path) -> None:
     """If an alternate copy_into method is provided, it is used."""
 
     target = PurePath("/container/test_cwd")
@@ -367,7 +373,7 @@ def test_copy_test_sources_alternate_copy_into(sample_project):
     )
 
 
-def test_unwrap():
+def test_unwrap() -> None:
     assert (
         unwrap("""
             This is a
@@ -378,7 +384,7 @@ def test_unwrap():
     )
 
 
-def test_unwrap_preserving_paragraphs():
+def test_unwrap_preserving_paragraphs() -> None:
     assert (
         unwrap("""
             This is a

unit_test/wheel_print_test.py

@@ -9,7 +9,7 @@ OPTIONS_DEFAULTS = Options("linux", CommandLineArguments.defaults(), {}, default
 FILE = Path(__file__)
 
 
-def test_printout_wheels(capsys):
+def test_printout_wheels(capsys: pytest.CaptureFixture[str]) -> None:
     log = Logger()
     log.fold_mode = "disabled"
     log.colors_enabled = False
@@ -32,7 +32,7 @@ def test_printout_wheels(capsys):
     assert "SHA256=" in captured.out
 
 
-def test_no_printout_on_error(capsys):
+def test_no_printout_on_error(capsys: pytest.CaptureFixture[str]) -> None:
     log = Logger()
     with pytest.raises(RuntimeError), log.print_summary(options=OPTIONS_DEFAULTS):
         raise RuntimeError()