[router] Introduce router integration tests (#10086)

sgl-router/py_test/integration/test_api_auth.py

@@ -0,0 +1,38 @@
+import pytest
+import requests
+
+
+@pytest.mark.integration
+def test_router_api_key_enforcement(router_manager, mock_workers):
+    # Start backend requiring API key; router should forward Authorization header transparently
+    _, urls, _ = mock_workers(
+        n=1, args=["--require-api-key", "--api-key", "correct_api_key"]
+    )
+    rh = router_manager.start_router(
+        worker_urls=urls,
+        policy="round_robin",
+        extra={},
+    )
+
+    # No auth -> 401
+    r = requests.post(
+        f"{rh.url}/v1/completions",
+        json={"model": "test-model", "prompt": "x", "max_tokens": 1, "stream": False},
+    )
+    assert r.status_code == 401
+
+    # Invalid auth -> 401
+    r = requests.post(
+        f"{rh.url}/v1/completions",
+        json={"model": "test-model", "prompt": "x", "max_tokens": 1, "stream": False},
+        headers={"Authorization": "Bearer wrong"},
+    )
+    assert r.status_code == 401
+
+    # Correct auth -> 200
+    r = requests.post(
+        f"{rh.url}/v1/completions",
+        json={"model": "test-model", "prompt": "x", "max_tokens": 1, "stream": False},
+        headers={"Authorization": "Bearer correct_api_key"},
+    )
+    assert r.status_code == 200