Add a test for construction of EnvironmentInfo.

conftest.py

@@ -1,3 +1,4 @@
+import platform
 import sys
 
 import pytest
@@ -67,3 +68,9 @@ def conditional_skip(request):
             pytest.skip("running integration tests only")
         if not running_integration_tests and is_integration_test:
             pytest.skip("skipping integration tests")
+
+
+@pytest.fixture
+def windows_only():
+    if platform.system() != 'Windows':
+        pytest.skip("Windows only")

setuptools/msvc.py

@@ -1,5 +1,8 @@
 """
 Environment info about Microsoft Compilers.
+
+>>> getfixture('windows_only')
+>>> ei = EnvironmentInfo('amd64')
 """
 
 from __future__ import annotations