Harden runtime compatibility policy checks

backend/tests/integration/test_api.py

@@ -1,9 +1,11 @@
 """Integration tests for API endpoints."""
 
+from importlib import metadata
+
 import pytest
 from fastapi.testclient import TestClient
 
-from backend.main import app
+from backend.main import app, compatibility_status
 
 client = TestClient(app)
 
@@ -49,8 +51,42 @@ class TestAPIIntegration:
         assert payload["ok"] is True
         assert payload["required_python"] == "3.14"
         assert "current_python" in payload
+        assert payload["python_policy_valid"] is True
         assert "required_packages" in payload
         assert payload["required_packages"]["fastapi"] == "0.120.2"
         assert payload["required_packages"]["uvicorn"] == "0.38.0"
+        assert payload["package_errors"] == {}
 
         monkeypatch.delenv("BACKEND_REQUIRED_PYTHON", raising=False)
+
+    def test_startup_rejects_malformed_required_python(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        """Startup should fail fast when Python policy is not strict major.minor."""
+        monkeypatch.setenv("BACKEND_REQUIRED_PYTHON", "3.14.1")
+
+        with pytest.raises(RuntimeError), TestClient(app):
+            pass
+
+        monkeypatch.delenv("BACKEND_REQUIRED_PYTHON", raising=False)
+
+    def test_compatibility_status_handles_missing_package_metadata(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        """Compatibility checks should handle missing package metadata gracefully."""
+
+        def raise_not_found(_: str) -> str:
+            raise metadata.PackageNotFoundError("fake")
+
+        monkeypatch.setattr("backend.main._installed_version", raise_not_found)
+        status = compatibility_status()
+        package_checks = status["package_checks"]
+        package_errors = status["package_errors"]
+
+        assert status["ok"] is False
+        assert isinstance(package_checks, dict)
+        assert isinstance(package_errors, dict)
+        assert package_checks["fastapi"] is False
+        assert package_checks["uvicorn"] is False
+        assert "fastapi" in package_errors
+        assert "uvicorn" in package_errors