add tests

tests/test_form_default.py

@@ -0,0 +1,46 @@
+from typing import Annotated, Optional
+
+from fastapi import FastAPI, File, Form
+from starlette.testclient import TestClient
+
+app = FastAPI()
+client = TestClient(app)
+
+
+@app.post("/urlencoded")
+async def post_url_encoded(age: Annotated[Optional[int], Form()] = None):
+    return age
+
+
+def test_form_default_url_encoded():
+    response = client.post("/urlencoded", data={"age": ""})
+    assert response.status_code == 200
+    assert response.text == "null"
+
+
+@app.post("/multipart")
+async def post_multi_part(
+    age: Annotated[Optional[int], Form()] = None,
+    file: Annotated[Optional[bytes], File()] = None,
+):
+    assert file is None
+    assert age is None
+
+
+def test_form_default_multi_part():
+    response = client.post("/multipart", data={"age": ""})
+    assert response.status_code == 200
+
+
+@app.post("/multipart-file-first")
+async def post_multi_part_file_first(
+    file: Annotated[Optional[bytes], File()] = None,
+    age: Annotated[Optional[int], Form()] = None,
+):
+    assert file is None
+    assert age is None
+
+
+def test_form_default_multi_part_file_first():
+    response = client.post("/multipart-file-first", data={"age": ""})
+    assert response.status_code == 200