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>

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()