8.6Test 4: Subgraph Health and Availability

    def test_all_subgraphs_healthy(self, subgraph_endpoints):
        """Each subgraph should respond to health checks."""
        for name, url in subgraph_endpoints.items():
            response = httpx.get(f"{url}/.well-known/apollo/server-health")
            assert response.status_code == 200, (
                f"Subgraph '{name}' at {url} is unhealthy: {response.status_code}"
            )

    def test_gateway_introspection(self, gateway_client):
        """Gateway should respond to introspection queries."""
        query = """
        {
          __schema {
            types { name }
            queryType { name }
          }
        }
        """
        response = gateway_client.execute(query)
        assert "errors" not in response
        type_names = [t["name"] for t in response["data"]["__schema"]["types"]]
        # Verify key types from each subgraph are present
        assert "Product" in type_names
        assert "Order" in type_names
        assert "User" in type_names