test: add test-integrity delta fixtures (#79)

Co-authored-by: Sam Valladares <143034159+samvallad33@users.noreply.github.com>

tests/hooks/test_sanhedrin_test_integrity_delta_fixtures.py

@@ -0,0 +1,82 @@
+import json
+from pathlib import Path
+import unittest
+
+
+FIXTURE_DIR = (
+    Path(__file__).resolve().parents[2]
+    / "docs"
+    / "fixtures"
+    / "sanhedrin-test-integrity-deltas"
+)
+
+
+class TestSanhedrinTestIntegrityDeltaFixtures(unittest.TestCase):
+    def test_fixture_receipts_are_executable_contract_examples(self):
+        fixtures = sorted(FIXTURE_DIR.glob("*.json"))
+        self.assertEqual(
+            [fixture.name for fixture in fixtures],
+            [
+                "justified-snapshot.json",
+                "skipped-test.json",
+                "unchanged-good.json",
+                "weakened-assertion.json",
+            ],
+        )
+
+        expected_decisions = {
+            "justified-snapshot": "needs_human_review",
+            "skipped-test": "downgraded",
+            "unchanged-good": "accepted",
+            "weakened-assertion": "downgraded",
+        }
+
+        for fixture in fixtures:
+            with self.subTest(fixture=fixture.name):
+                data = json.loads(fixture.read_text(encoding="utf-8"))
+                receipt = data["receipt"]
+
+                self.assertEqual(
+                    receipt["schema"],
+                    "vestige.sanhedrin.test_integrity_delta.v1",
+                )
+                self.assertEqual(data["expectedDecision"], receipt["decision"])
+                self.assertEqual(expected_decisions[data["case"]], receipt["decision"])
+                self.assertTrue(receipt["freshVerifier"]["checkedAfterLastRelevantEdit"])
+                self.assertEqual(receipt["freshVerifier"]["exitCode"], 0)
+
+                test_files = receipt["specSource"]["testFiles"]
+                self.assertGreaterEqual(len(test_files), 1)
+                for test_file in test_files:
+                    self.assertTrue(test_file["path"])
+                    self.assertRegex(
+                        test_file["hashBeforeImplementation"],
+                        r"^sha256:[0-9a-f]{64}$",
+                    )
+                    self.assertRegex(
+                        test_file["hashAfterVerification"],
+                        r"^sha256:[0-9a-f]{64}$",
+                    )
+
+    def test_downgrade_fixtures_have_mechanical_downgrade_evidence(self):
+        for fixture in sorted(FIXTURE_DIR.glob("*.json")):
+            data = json.loads(fixture.read_text(encoding="utf-8"))
+            if data["expectedDecision"] != "downgraded":
+                continue
+
+            delta = data["receipt"]["delta"]
+            has_downgrade_evidence = any(
+                [
+                    delta["removedOrDisabledTests"],
+                    delta["removedAssertions"] > 0,
+                    delta["weakenedExpectations"],
+                    delta["snapshotChurnWithoutSourceChange"],
+                    delta["coverageDelta"] < 0,
+                    delta["mocksReplacingRealBoundary"],
+                ]
+            )
+            self.assertTrue(has_downgrade_evidence, data["case"])
+
+
+if __name__ == "__main__":
+    unittest.main()