Fix test for Windows

Author: nedbat

tests/test_pytest_cov.py

@@ -1996,8 +1996,10 @@ def test_contexts(testdir, opts):
     data = coverage.CoverageData(".coverage")
     data.read()
     assert data.measured_contexts() == set(EXPECTED_CONTEXTS)
-    test_context_path = os.path.abspath("test_contexts.py")
-    assert data.measured_files() == {test_context_path}
+    measured = data.measured_files()
+    assert len(measured) == 1
+    test_context_path = list(measured)[0]
+    assert test_context_path.lower() == os.path.abspath("test_contexts.py").lower()
 
     line_data = find_labels(contextful_tests, r"[crst]\d+(?:-\d+)?")
     for context, label in EXPECTED_CONTEXTS.items():