✅ Add test for deprecated openapi_prefix

tests/test_deprecated_openapi_prefix.py

@@ -0,0 +1,43 @@
+from fastapi import FastAPI, Request
+from fastapi.testclient import TestClient
+
+app = FastAPI(openapi_prefix="/api/v1")
+
+
+@app.get("/app")
+def read_main(request: Request):
+    return {"message": "Hello World", "root_path": request.scope.get("root_path")}
+
+
+client = TestClient(app)
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "paths": {
+        "/api/v1/app": {
+            "get": {
+                "summary": "Read Main",
+                "operationId": "read_main_app_get",
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {"application/json": {"schema": {}}},
+                    }
+                },
+            }
+        }
+    },
+}
+
+
+def test_openapi():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200
+    assert response.json() == openapi_schema
+
+
+def test_main():
+    response = client.get("/app")
+    assert response.status_code == 200
+    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}