> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Create User Test
> This article explains how to create tests for user creation functionality in a FastAPI application using TestClient.
In this lesson, we will create tests to verify the user creation functionality of our API using FastAPI’s TestClient. We simulate GET and POST requests to ensure that the API responds correctly.
***
## Testing the Root Endpoint
Before testing user creation, we first verify that the API's root endpoint is operational. The following test sends a GET request to the "/" route and asserts that the response includes the message "Hello World" with a status code of 200.
```python theme={null}
from fastapi.testclient import TestClient
from app.main import app
client = TestClient(app)
def test_root():
res = client.get("/")
print(res.json().get("message"))
assert res.json().get("message") == "Hello World"
assert res.status_code == 200
```
Sample console output:
```plaintext theme={null}
tests/test_calculations.py::test_bank_transaction[50-10-40] PASSED
tests/test_calculations.py::test_bank_transaction[1200-200-1000] PASSED
tests/test_calculations.py::test_insufficient_funds PASSED
tests/test_users.py::test_root PASSED
============================= 16 passed, 5 warnings in 0.67s =============================
```
***
## Testing the Create User Endpoint
Next, we validate the user creation route. This route expects a POST request to `/users/` with JSON data containing an email and a password.
Initially, a simple version of the test might look like this:
```python theme={null}
from fastapi.testclient import TestClient
def register():
r = 'Hello World'
```
Sample output for test runs:
```plaintext theme={null}
tests/test_calculations.py::test_bank_transaction[50-10-40] PASSED
tests/test_calculations.py::test_bank_transaction[1200-200-1000] PASSED
tests/test_calculations.py::test_insufficient_funds PASSED
tests/test_users.py::test_root PASSED
============================== 16 passed, 5 warnings in 0.67s ===============================
```
Now, update the test to send a POST request with a JSON payload. In our endpoint, the schema requires an email and password. We verify that the response status is 201 (Created).
```python theme={null}
from fastapi.testclient import TestClient
from app.main import app
client = TestClient(app)
def test_create_user():
res = client.post("/users/", json={"email": "hello123@gmail.com", "password": "password123"})
print(res.json())
assert res.status_code == 201
```
The test output should confirm a status code of 201:
```plaintext theme={null}
tests/test_calculations.py::test_bank_transaction[50-10-40] PASSED
tests/test_calculations.py::test_bank_transaction[1200-200-1000] PASSED
tests/test_calculations.py::test_insufficient_funds PASSED
tests/test_users.py::test_root PASSED
================================== 16 passed, 5 warnings in 0.67s ===================================
```
***
## Validating the Response Schema
The user creation endpoint is designed to return data that follows a specific schema, including an ID, email, and a created\_at timestamp. The expected Pydantic model is defined as follows:
```python theme={null}
from pydantic import BaseModel, EmailStr
from datetime import datetime
class PostCreate(PostBase):
pass
class UserOut(BaseModel):
id: int
email: EmailStr
created_at: datetime
class Config:
orm_mode = True
class Post(PostBase):
pass
```
To ensure that the response conforms to this schema, the test imports the schemas and instantiates a `UserOut` model with the returned JSON data. This method automatically validates the structure of the response.
```python theme={null}
from fastapi.testclient import TestClient
from app.main import app
from app import schemas # Import schemas to use the UserOut model
client = TestClient(app)
def test_create_user():
res = client.post(
"/users/", json={"email": "hello123@gmail.com", "password": "password123"}
)
# Validate the response using the UserOut schema
new_user = schemas.UserOut(**res.json())
# Confirm that the email is correct and the status code is 201
assert new_user.email == "hello123@gmail.com"
assert res.status_code == 201
```
Running this test will produce output similar to:
```plaintext theme={null}
tests/test_users.py::test_root Hello World
PASSED
tests/test_users.py::test_create_user {'id': 12, 'email': 'hello123@gmail.com', 'created_at': '2021-09-12T21:29:59.775700-04:00'}
PASSED
================================= 2 passed, 5 warnings in 0.89s =================================
```
***
## Handling Duplicate User Creation
At times, using the same email for multiple tests can trigger an IntegrityError due to a duplicate key violation. An example error message might be:
```plaintext theme={null}
cursor.execute(statement, parameters)
sqlalchemy.exc.IntegrityError: (psycopg2.errors.UniqueViolation) duplicate key value violates unique constraint "users_email_key"
DETAIL: Key (email)=(hello123@gmail.com) already exists.
...
```
To avoid duplicate key errors, ensure that users are either removed from the database between tests or that you use unique email addresses for each test run.
You can run the following SQL command in PgAdmin to view current user entries:
```sql theme={null}
SELECT * FROM public.users
ORDER BY "id" ASC;
```
After deleting the user entry with the email "[hello123@gmail.com](mailto:hello123@gmail.com)", re-running the test should result in a successful user creation.
***
## Final Test Code
Below is the consolidated version of our test code after all improvements:
```python theme={null}
from fastapi.testclient import TestClient
from app.main import app
from app import schemas
client = TestClient(app)
def test_root():
res = client.get("/")
print(res.json().get("message"))
assert res.json().get("message") == "Hello World"
assert res.status_code == 200
def test_create_user():
res = client.post(
"/users/", json={"email": "hello123@gmail.com", "password": "password123"}
)
new_user = schemas.UserOut(**res.json())
assert new_user.email == "hello123@gmail.com"
assert res.status_code == 201
```
Sample run confirming both tests pass:
```plaintext theme={null}
platform win32 -- Python 3.9.5, pytest-6.2.5, py-1.10.0, pluggy-1.0.0 -- c:\users\sanje\documents\courses\fastapi\venv\scripts\python.exe
cachedir: .pytest_cache
rootdir: c:\Users\sanje\Documents\Courses\fastapi
plugins: cov-2.12.1
collected 2 items
tests/test_users.py::test_root Hello World PASSED
tests/test_users.py::test_create_user PASSED
================================== 2 passed, 5 warnings in 0.87s ==================================
```
This approach leverages FastAPI's TestClient and Pydantic for automatic schema validation, reducing the need for multiple manual assertions and ensuring the correctness of the API responses.