test(registry-check): add failing test for registry-fetch smoke check

- RED phase: test_registry_check.py covers all-200 success, one-404
  failure, network-unavailable distinction, HTTP 5xx errors, and CLI
  exit-code paths for the not-yet-implemented cas_evals.registry_check
- REQ-1.4.11

Author: Aitomates

tests/test_registry_check.py

@@ -0,0 +1,95 @@
+import io
+import unittest
+from contextlib import redirect_stdout
+from unittest.mock import MagicMock, patch
+from urllib.error import HTTPError, URLError
+
+from cas_evals.registry_check import RegistryCheckError, check_registry_urls, main
+
+
+def _fake_response(status_code):
+    response = MagicMock()
+    response.status = status_code
+    response.read.return_value = b""
+    response.__enter__.return_value = response
+    response.__exit__.return_value = False
+    return response
+
+
+class RegistryCheckTests(unittest.TestCase):
+    def test_all_paths_return_200(self):
+        with patch("cas_evals.registry_check.urlopen", return_value=_fake_response(200)) as urlopen:
+            results = check_registry_urls(
+                "https://coding-autopilot-system.github.io/cas-contracts/registry",
+                ["index.json", "v0.1/manifest.json"],
+            )
+        self.assertEqual(
+            results,
+            [("index.json", 200), ("v0.1/manifest.json", 200)],
+        )
+        self.assertEqual(urlopen.call_count, 2)
+
+    def test_one_path_returns_404(self):
+        responses = [_fake_response(200), _fake_response(404)]
+
+        def side_effect(*args, **kwargs):
+            return responses.pop(0)
+
+        with patch("cas_evals.registry_check.urlopen", side_effect=side_effect):
+            with self.assertRaises(RegistryCheckError) as ctx:
+                check_registry_urls(
+                    "https://coding-autopilot-system.github.io/cas-contracts/registry",
+                    ["index.json", "v0.1/manifest.json"],
+                )
+        self.assertIn("v0.1/manifest.json", str(ctx.exception))
+        self.assertIn("404", str(ctx.exception))
+
+    def test_network_unavailable_raises_distinguishable_error(self):
+        with patch("cas_evals.registry_check.urlopen", side_effect=URLError("no route to host")):
+            with self.assertRaises(RegistryCheckError) as ctx:
+                check_registry_urls(
+                    "https://coding-autopilot-system.github.io/cas-contracts/registry",
+                    ["index.json"],
+                )
+        self.assertIn("unavailable", str(ctx.exception).lower())
+        self.assertNotIn("404", str(ctx.exception))
+
+    def test_http_error_raises_registry_check_error(self):
+        error = HTTPError("https://example.com/index.json", 500, "Internal Server Error", {}, None)
+        with patch("cas_evals.registry_check.urlopen", side_effect=error):
+            with self.assertRaises(RegistryCheckError) as ctx:
+                check_registry_urls(
+                    "https://coding-autopilot-system.github.io/cas-contracts/registry",
+                    ["index.json"],
+                )
+        self.assertIn("500", str(ctx.exception))
+
+    def test_main_exits_zero_on_success(self):
+        with patch("cas_evals.registry_check.check_registry_urls") as mocked:
+            mocked.return_value = [
+                ("index.json", 200),
+                ("v0.1/manifest.json", 200),
+                ("v0.1/common.schema.json", 200),
+                ("v0.1/evaluation-result.schema.json", 200),
+            ]
+            buffer = io.StringIO()
+            with redirect_stdout(buffer):
+                exit_code = main([])
+        self.assertEqual(exit_code, 0)
+        output = buffer.getvalue()
+        self.assertIn("index.json", output)
+        self.assertIn("200", output)
+
+    def test_main_exits_nonzero_on_failure(self):
+        with patch(
+            "cas_evals.registry_check.check_registry_urls",
+            side_effect=RegistryCheckError("v0.1/manifest.json returned HTTP 404"),
+        ):
+            buffer = io.StringIO()
+            with redirect_stdout(buffer):
+                exit_code = main([])
+        self.assertEqual(exit_code, 1)
+
+
+if __name__ == "__main__":
+    unittest.main()