Remove the flag that lets a run report skips as acceptable

tests/test_test_outcome.py

@@ -141,5 +141,32 @@ def test_a_vstest_run_over_an_empty_assembly_names_no_dialect(self):
         self.assertIsNone(outcome.read_summaries(log)[2])
 
 
+class NoFlagPermitsASkipTests(unittest.TestCase):
+    """No option tolerates a skip, and none may be added back.
+
+    A flag that makes skips acceptable is the whole rule's escape hatch: the
+    repository holding it can pass the flag and report success over a suite that
+    covers nothing. Refusing the flag at the parser is what makes the rule
+    unconditional, and this test is what keeps it refused."""
+
+    def _parser_options(self):
+        parser = outcome.build_parser()
+        return {opt for action in parser._actions for opt in action.option_strings}
+
+    def test_the_parser_offers_no_option_tolerating_a_skip(self):
+        options = self._parser_options()
+        # A positive control: the parser is real and does carry its own options.
+        self.assertIn("--min-tests", options)
+        permissive = {o for o in options
+                      if "skip" in o.lower() or "ignore" in o.lower()}
+        self.assertEqual(set(), permissive)
+
+    def test_a_skip_fails_whatever_the_floor(self):
+        log = ("Passed!  - Failed:     0, Passed:    66, Skipped:     1, "
+               "Total:    67, Duration: 1 s - Suite.dll (net8.0)\n")
+        total, skipped, dialect, _ = outcome.read_summaries(log)
+        self.assertEqual(("vstest", 67, 1), (dialect, total, skipped))
+
+
 if __name__ == "__main__":
     unittest.main()

tools/check-test-outcome.py

@@ -44,7 +44,7 @@
 # consumer tees must come from `go test -v`.
 #
 # Usage:
-#   tools/check-test-outcome.py <build.log> [--min-tests N] [--allow-skips]
+#   tools/check-test-outcome.py <build.log> [--min-tests N]
 #
 # Exit status is 0 when the log satisfies both rules and 1 otherwise.
 
@@ -176,14 +176,22 @@ def read_summaries(text: str):
     return 0, 0, None, []
 
 
-def main() -> int:
+def build_parser() -> argparse.ArgumentParser:
+    """The command line, as its own function so a test can read the options.
+
+    There is deliberately no option that tolerates a skip. A flag permitting one
+    is the rule's escape hatch — the repository holding it passes the flag and
+    reports success over a suite that covers nothing — so the absence is a
+    property the suite asserts rather than a convention."""
     ap = argparse.ArgumentParser(description=__doc__)
     ap.add_argument("log", help="build log carrying the test summary")
     ap.add_argument("--min-tests", type=int, default=0,
                     help="floor the total may not fall below")
-    ap.add_argument("--allow-skips", action="store_true",
-                    help="report skips without failing (never in CI)")
-    args = ap.parse_args()
+    return ap
+
+
+def main() -> int:
+    args = build_parser().parse_args()
 
     path = Path(args.log)
     if not path.exists():
@@ -209,7 +217,7 @@ def main() -> int:
 
     failed = False
 
-    if skipped and not args.allow_skips:
+    if skipped:
         for line in text.splitlines():
             s = line.strip()
             if (s.startswith("SKIPPED") or " SKIPPED " in s
@@ -230,13 +238,6 @@ def main() -> int:
 
     if failed:
         return 1
-    if skipped:
-        # Only --allow-skips reaches here with a non-zero count, and saying
-        # "nothing skipped" over it would misreport the one run that tolerates
-        # them.
-        print(f"check-test-outcome: {skipped} skipped, tolerated by "
-              f"--allow-skips; the suite did not shrink")
-        return 0
     print("check-test-outcome: nothing skipped, and the suite did not shrink")
     return 0