Add test for cross-compile testing behaviour

test/test_macos_archs.py

@@ -1,4 +1,5 @@
 import pytest
+import platform
 
 from . import test_projects, utils
 
@@ -15,13 +16,52 @@ def test_cross_compiled_build(tmp_path):
     basic_project.generate(project_dir)
 
     actual_wheels = utils.cibuildwheel_run(project_dir, add_env={
+        'CIBW_BUILD': 'cp39-*',
         'CIBW_ARCHS': 'x86_64, universal2, arm64',
     })
 
-    expected_wheels = (
+    all_macos_wheels = (
         utils.expected_wheels('spam', '0.1.0', machine_arch='x86_64')
         + utils.expected_wheels('spam', '0.1.0', machine_arch='arm64')
     )
+
+    # only cpython 3.9
+    expected_wheels = [w for w in all_macos_wheels if 'cp39' in w]
     assert set(actual_wheels) == set(expected_wheels)
 
+
+@pytest.mark.parametrize('build_universal2', [False, True])
+def test_cross_compiled_test(tmp_path, capfd, build_universal2):
+    if utils.platform != 'macos':
+        pytest.skip('this test is only relevant to macos')
+    if utils.get_macos_version() < (11, 0):
+        pytest.skip('this test only works on macOS 11 or greater')
+
+    project_dir = tmp_path / 'project'
+    basic_project.generate(project_dir)
+
+    actual_wheels = utils.cibuildwheel_run(project_dir, add_env={
+        'CIBW_BUILD': 'cp39-*',
+        'CIBW_TEST_COMMAND': '''python -c "import platform; print('running tests on ' + platform.machine())"''',
+        'CIBW_ARCHS': 'universal2' if build_universal2 else 'x86_64 arm64',
+    })
+
+    captured = capfd.readouterr()
+
+    if platform.machine() == 'x86_64':
+        # ensure that tests were run on only x86_64
+        assert 'running tests on x86_64' in captured.out
+        assert 'running tests on arm64' not in captured.out
+        if build_universal2:
+            assert 'While universal2 wheels can be built on x86_64, the arm64 part of them cannot currently be tested' in captured.out
+        else:
+            assert 'While arm64 wheels can be built on x86_64, they cannot be tested' in captured.out
+    elif platform.machine() == 'arm64':
+        # ensure that tests were run on both x86_64 and arm64
+        assert 'running tests on x86_64' in captured.out
+        assert 'running tests on arm64' in captured.out
+
+    print(actual_wheels)
+
+
 # TODO: add a TEST_COMMAND test when using cross-compiling