From af9de5204b62b4b52de9f129cca5893607d4c8e7 Mon Sep 17 00:00:00 2001
From: Yurii Motov <yurii.motov.monte@gmail.com>
Date: Thu, 6 Nov 2025 14:22:01 +0100
Subject: [PATCH] Add test

---
 tests/test_forms_single_model.py | 47 ++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/tests/test_forms_single_model.py b/tests/test_forms_single_model.py
index 880ab3820..1db63f021 100644
--- a/tests/test_forms_single_model.py
+++ b/tests/test_forms_single_model.py
@@ -2,6 +2,7 @@ from typing import List, Optional
 
 from dirty_equals import IsDict
 from fastapi import FastAPI, Form
+from fastapi._compat import PYDANTIC_V2
 from fastapi.testclient import TestClient
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
@@ -17,11 +18,27 @@ class FormModel(BaseModel):
     alias_with: str = Field(alias="with", default="nothing")
 
 
+class FormModelExtraAllow(BaseModel):
+    param: str
+
+    if PYDANTIC_V2:
+        model_config = {"extra": "allow"}
+    else:
+
+        class Config:
+            extra = "allow"
+
+
 @app.post("/form/")
 def post_form(user: Annotated[FormModel, Form()]):
     return user
 
 
+@app.post("/form-extra-allow/")
+def post_form_extra_allow(params: Annotated[FormModelExtraAllow, Form()]):
+    return params
+
+
 client = TestClient(app)
 
 
@@ -131,3 +148,33 @@ def test_no_data():
             ]
         }
     )
+
+
+def test_extra_param_single():
+    response = client.post(
+        "/form-extra-allow/",
+        data={
+            "param": "123",
+            "extra_param": "456",
+        },
+    )
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "param": "123",
+        "extra_param": "456",
+    }
+
+
+def test_extra_param_list():
+    response = client.post(
+        "/form-extra-allow/",
+        data={
+            "param": "123",
+            "extra_params": ["456", "789"],
+        },
+    )
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "param": "123",
+        "extra_params": ["456", "789"],
+    }