Test empty responses value

tests/test_additional_response_empty.py

@@ -0,0 +1,69 @@
+from typing import Dict
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class Items(BaseModel):
+    items: Dict[str, int]
+
+
+@app.post("/foo", responses={422: {}})
+def foo(items: Items):
+    return items.items
+
+
+client = TestClient(app)
+
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "paths": {
+        "/foo": {
+            "post": {
+                "summary": "Foo",
+                "operationId": "foo_foo_post",
+                "requestBody": {
+                    "content": {
+                        "application/json": {
+                            "schema": {"$ref": "#/components/schemas/Items"}
+                        }
+                    },
+                    "required": True,
+                },
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {"application/json": {"schema": {}}},
+                    }
+                },
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "Items": {
+                "title": "Items",
+                "required": ["items"],
+                "type": "object",
+                "properties": {
+                    "items": {
+                        "title": "Items",
+                        "type": "object",
+                        "additionalProperties": {"type": "integer"},
+                    }
+                },
+            }
+        }
+    },
+}
+
+
+def test_additional_properties_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == openapi_schema