diff --git a/unit_test/main_function_test.py b/unit_test/main_function_test.py
new file mode 100644
index 00000000..d2e48a3f
--- /dev/null
+++ b/unit_test/main_function_test.py
@@ -0,0 +1,263 @@
+import sys
+import os
+import subprocess
+
+import pytest
+
+from cibuildwheel.__main__ import main
+from cibuildwheel import windows, linux, macos
+from cibuildwheel.util import BuildSelector
+from cibuildwheel.environment import ParsedEnvironment
+
+@pytest.fixture
+def argtest():
+    class TestArgs(object):
+        def __call__(self, **kwargs): 
+            self.kwargs = dict(kwargs)
+    return TestArgs()
+
+def not_call_mock(*args, **kwargs):
+    raise RuntimeError("This should never be called")
+
+
+def apply_mock_protection(monkeypatch):
+    monkeypatch.setattr(subprocess, "Popen", not_call_mock)
+    monkeypatch.setattr(windows, "urlopen", not_call_mock)
+    monkeypatch.setattr(windows, "build", not_call_mock)
+    monkeypatch.setattr(linux, "build", not_call_mock)
+    monkeypatch.setattr(macos, "build", not_call_mock)
+    monkeypatch.setattr(os.path, "exists", lambda x: True)
+    monkeypatch.setattr(sys, "argv", ["python", "abcabc"])
+
+
+def test_unknown_platform_non_ci(monkeypatch, capsys):
+    monkeypatch.setattr(os, 'environ', {})
+    apply_mock_protection(monkeypatch)
+    with pytest.raises(SystemExit) as exit:
+        main()
+    assert exit.value.code == 2
+    _, err = capsys.readouterr()
+    assert 'cibuildwheel: Unable to detect platform.' in err
+    assert "cibuildwheel should run on your CI server" in err
+
+
+def test_unknown_platform_on_ci(monkeypatch, capsys):
+    monkeypatch.setattr(os, 'environ', {"CI": "true"})
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(sys, "platform", "Something")
+
+    with pytest.raises(SystemExit) as exit:
+        main()
+    _, err = capsys.readouterr()
+    assert exit.value.code == 2
+    assert 'cibuildwheel: Unable to detect platform from "sys.platform"' in err
+
+
+def test_unknown_platform(monkeypatch, capsys):
+    monkeypatch.setattr(os, 'environ', {"CIBW_PLATFORM": "Something"})
+    apply_mock_protection(monkeypatch)
+    with pytest.raises(SystemExit) as exit:
+        main()
+    _, err = capsys.readouterr()
+    assert exit.value.code == 2
+    assert 'cibuildwheel: Unsupported platform: Something' in err
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("choose_platform_method", ["partameter", "environment"])
+def test_platform_chose(system, choose_platform_method, argtest, monkeypatch):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    if choose_platform_method == "partameter":
+        monkeypatch.setattr(sys, "argv", sys.argv + ["--platform", system])
+    else:
+        monkeypatch.setattr(os, 'environ', {"CIBW_PLATFORM": system})
+    main()
+    assert argtest.kwargs["project_dir"] == "abcabc"
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("output_dir", ["partameter", "environment", "both", "none"])
+def test_output_dir_set(system, output_dir, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    output_name = "out"
+    env = {"CIBW_PLATFORM": system}
+    if output_dir == "partameter":
+        monkeypatch.setattr(sys, "argv", sys.argv + ["--output-dir", output_name])
+    elif output_dir == "environment":
+        env["CIBW_OUTPUT_DIR"] = output_name
+    elif output_dir == "both":
+        monkeypatch.setattr(sys, "argv", sys.argv + ["--output-dir", output_name])
+        env["CIBW_OUTPUT_DIR"] = output_name + "aaa"
+    else:
+        output_name = "wheelhouse"
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert argtest.kwargs["output_dir"] == output_name
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("build,build_set", [
+    ("*", {"aaaa", "abcd", "abab", "bcde"}),
+    ("a*", {"aaaa", "abcd", "abab"}),
+    ("*b*", {"abcd", "abab", "bcde"})
+    ])
+@pytest.mark.parametrize("skip,skip_set", [
+    ("", set()), ("a*", {"aaaa", "abcd", "abab"}),
+    ("*c*", {"abcd", "bcde"})
+])
+def test_build_selector(system, build, build_set, skip, skip_set, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system, "CIBW_BUILD": build, "CIBW_SKIP": skip}
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert isinstance(argtest.kwargs["build_selector"], BuildSelector)
+    selector = argtest.kwargs["build_selector"]
+    selected = set([x for x in ["aaaa", "abcd", "abab", "bcde"] if selector(x)])
+    assert selected == build_set.difference(skip_set)
+
+
+@pytest.mark.parametrize("system", ["macos", "windows"])
+@pytest.mark.parametrize("manylinux", ["none", "manylinux1"])
+def test_no_manylinux(system, manylinux, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system}
+    if manylinux != "none":
+        env["CIBW_MANYLINUX_I686_IMAGE"] = manylinux
+        env["CIBW_MANYLINUX_X86_64_IMAGE"] = manylinux
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert "manylinux_images" not in argtest.kwargs
+
+
+@pytest.mark.parametrize("manylinux86,manylinux86_image", [
+    ("none", 'quay.io/pypa/manylinux2010_i686'), 
+    ("manylinux1", 'quay.io/pypa/manylinux1_i686'),
+    ("manylinux2010", 'quay.io/pypa/manylinux2010_i686'),
+    ("asfsgd", "asfsgd")])
+@pytest.mark.parametrize("manylinux64, manylinux64_image", [
+    ("none", 'quay.io/pypa/manylinux2010_x86_64'), 
+    ("manylinux1", 'quay.io/pypa/manylinux1_x86_64'),
+    ("manylinux2010", 'quay.io/pypa/manylinux2010_x86_64'),
+    ("asfsgd", "asfsgd")])
+def test_manylinux_choose(manylinux86, manylinux86_image, manylinux64,
+        manylinux64_image, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(linux, "build", argtest)
+    env = {"CIBW_PLATFORM": "linux"}
+    if manylinux86 != "none":
+        env["CIBW_MANYLINUX_I686_IMAGE"] = manylinux86
+    if manylinux64 != "none":
+        env["CIBW_MANYLINUX_X86_64_IMAGE"] = manylinux64
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert argtest.kwargs["manylinux_images"]['x86_64'] == manylinux64_image
+    assert argtest.kwargs["manylinux_images"]['i686'] == manylinux86_image
+
+
+@pytest.mark.parametrize("system,default_repair", [
+    ("macos", "delocate"), ("linux", "auditwheel"),
+    ("windows", "")])
+@pytest.mark.parametrize("repair_command", ["none", "aaaa", "repair -w {dest_dir} {wheel}"])
+@pytest.mark.parametrize("system_suffix", (True, False))
+def test_repair_command(system, default_repair, repair_command, system_suffix, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system}
+    if repair_command != "none":
+        env["CIBW_REPAIR_WHEEL_COMMAND"] = repair_command
+    if system_suffix:
+        env["CIBW_REPAIR_WHEEL_COMMAND_" + system.upper()] = "abcabc"
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    if system_suffix:
+        assert argtest.kwargs["repair_command"] == "abcabc"
+    elif repair_command == "none":
+        if default_repair:
+            assert argtest.kwargs["repair_command"].startswith(default_repair)
+        else:
+            assert len(argtest.kwargs["repair_command"]) == 0
+    else:
+        assert argtest.kwargs["repair_command"] == repair_command
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("environment", [{}, {"AAA": "123"}, {"AA1": "124", "AA2": "124"}])
+@pytest.mark.parametrize("platform_environment", [{}, {"BBB": "123"}, {"BB1": "123", "BB2": "127"}])
+def test_environment(system, environment, platform_environment, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system}
+    cibw_env = " ".join(["{}={}".format(k, v) for k, v in environment.items()])
+    platform_env = " ".join(["{}={}".format(k, v) for k, v in platform_environment.items()])
+    if cibw_env:
+        env["CIBW_ENVIRONMENT"] = cibw_env
+    if platform_env:
+        env["CIBW_ENVIRONMENT_{}".format(system.upper())] = platform_env
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert isinstance(argtest.kwargs["environment"], ParsedEnvironment)
+    if platform_environment:
+        assert argtest.kwargs["environment"].as_dictionary({}) == platform_environment
+    else:
+        assert argtest.kwargs["environment"].as_dictionary({}) == environment
+
+
+def identity(x):
+    return x
+
+
+def extras(x):
+    if x is None:
+        return ""
+    return "[{}]".format(x)
+
+
+def requires(x):
+    if x is None:
+        return []
+    return x.split()
+
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("generic_var", [None, "test1"])
+@pytest.mark.parametrize("platform_generic_var", [None, "test2"])
+@pytest.mark.parametrize("environ_var,kwargs_var,transform_var", [
+    ("CIBW_BEFORE_BUILD", "before_build", identity), ("CIBW_TEST_COMMAND", "test_command", identity),
+    ("CIBW_TEST_EXTRAS", "test_extras", extras), ("CIBW_TEST_REQUIRES", "test_requires", requires)])
+def test_generic_var(system, generic_var, platform_generic_var, environ_var, kwargs_var, transform_var, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system}
+    if generic_var:
+        env[environ_var] = generic_var
+    if platform_generic_var:
+        env["{}_{}".format(environ_var, system.upper())] = platform_generic_var
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert isinstance(argtest.kwargs["environment"], ParsedEnvironment)
+    if platform_generic_var:
+        assert argtest.kwargs[kwargs_var] == transform_var(platform_generic_var)
+    else:
+        assert argtest.kwargs[kwargs_var] == transform_var(generic_var)
+
+
+@pytest.mark.parametrize("system", ["macos", "linux", "windows"])
+@pytest.mark.parametrize("verbosity", [None, 0, -2, 4])
+@pytest.mark.parametrize("platform_verbosity", [None, 0, 2, -4])
+def test_build_verbosity(system, verbosity, platform_verbosity, monkeypatch, argtest):
+    apply_mock_protection(monkeypatch)
+    monkeypatch.setattr(globals()[system], "build", argtest)
+    env = {"CIBW_PLATFORM": system}
+    if verbosity is not None:
+        env["CIBW_BUILD_VERBOSITY"] = verbosity
+    if platform_verbosity is not None:
+        env["CIBW_BUILD_VERBOSITY_{}".format(system.upper())] = platform_verbosity
+    monkeypatch.setattr(os, 'environ', env)
+    main()
+    assert isinstance(argtest.kwargs["environment"], ParsedEnvironment)
+    if platform_verbosity is not None:
+        assert argtest.kwargs["build_verbosity"] == platform_verbosity if platform_verbosity > -4 else -3
+    elif verbosity is not None:
+        assert argtest.kwargs["build_verbosity"] == verbosity if verbosity < 4 else 3
+    else:
+        assert argtest.kwargs["build_verbosity"] == 0
\ No newline at end of file
diff --git a/unit_test/platform_test.py b/unit_test/platform_test.py
deleted file mode 100644
index f4199cc2..00000000
--- a/unit_test/platform_test.py
+++ /dev/null
@@ -1,59 +0,0 @@
-import sys
-import os
-import subprocess
-
-import pytest
-
-from cibuildwheel.__main__ import main
-from cibuildwheel import windows, linux, macos
-
-
-def not_call_mock(*args, **kwargs):
-    raise RuntimeError("This should never be called")
-
-
-def apply_mock_protection(monkeypatch):
-    monkeypatch.setattr(subprocess, "Popen", not_call_mock)
-    monkeypatch.setattr(windows, "urlopen", not_call_mock)
-    monkeypatch.setattr(windows, "build", not_call_mock)
-    monkeypatch.setattr(linux, "build", not_call_mock)
-    monkeypatch.setattr(macos, "build", not_call_mock)
-
-
-def test_unknown_platform_non_ci(monkeypatch, capsys, tmp_path):
-    monkeypatch.setattr(os, 'environ', {})
-    monkeypatch.setattr(sys, "argv", ["python", str(tmp_path)])
-    apply_mock_protection(monkeypatch)
-    with pytest.raises(SystemExit) as exit:
-        main()
-    assert exit.value.code == 2
-    _, err = capsys.readouterr()
-    assert 'cibuildwheel: Unable to detect platform.' in err
-    assert "cibuildwheel should run on your CI server" in err
-
-
-def test_unknown_platform_on_ci(monkeypatch, capsys, tmp_path):
-    monkeypatch.setattr(os, 'environ', {"CI": "true"})
-    monkeypatch.setattr(sys, "argv", ["python", str(tmp_path)])
-    apply_mock_protection(monkeypatch)
-    monkeypatch.setattr(sys, "platform", "Something")
-
-    with pytest.raises(SystemExit) as exit:
-        main()
-    _, err = capsys.readouterr()
-    assert exit.value.code == 2
-    assert 'cibuildwheel: Unable to detect platform from "sys.platform"' in err
-
-
-def test_unknown_platform(monkeypatch, capsys, tmp_path):
-    monkeypatch.setattr(os, 'environ', {"CIBW_PLATFORM": "Something"})
-    monkeypatch.setattr(sys, "argv", ["python", str(tmp_path)])
-    apply_mock_protection(monkeypatch)
-    with open(str(tmp_path / "setup.py"), "w") as f:
-        f.write('from setuptools import setup\nsetup(name="spam", version="0.1.0",)')
-
-    with pytest.raises(SystemExit) as exit:
-        main()
-    _, err = capsys.readouterr()
-    assert exit.value.code == 2
-    assert 'cibuildwheel: Unsupported platform: Something' in err