write tests using pytest for a MongoDB

write tests using pytest for a MongoDB user login check, you’ll need to create a sample database, add test data, and then write test cases to check the user login function. Here’s how you can do it:

Step 1: Install Required Packages
First, make sure you have pytest and mongomock installed. mongomock is a library that provides a mock in-memory MongoDB server for testing purposes:

pip install pytest mongomock

Step 2: Create Test Directory Structure
Create a directory structure for your tests. For example:

project_directory/
├── app/
│   └── checkuser.py  # Your user login code
└── tests/
    ├── conftest.py   # Configuration for pytest fixtures
    └── test_checkuser.py  # Test cases for user login

Step 3: Write Test Cases
In the test_checkuser.py file, write your test cases using pytest and the mongomock library:

import pytest
from mongomock import MongoClient
from app.checkuser import login  # Import your user login function

# Define a fixture to create a mock MongoDB client and populate test data
@pytest.fixture
def mock_mongo_client():
    mock_client = MongoClient()
    mock_db = mock_client['testdb']
    users_collection = mock_db['users']

    # Add test data
    users_collection.insert_one({'username': 'user1', 'password': 'hashed_password1'})
    users_collection.insert_one({'username': 'user2', 'password': 'hashed_password2'})

    return mock_client

# Test user login function
def test_login_valid_user(mock_mongo_client):
    # Call the login function with valid credentials
    user = login('user1', 'password1', mock_mongo_client)

    # Assert that the user is not None
    assert user is not None
    assert user['username'] == 'user1'

def test_login_invalid_user(mock_mongo_client):
    # Call the login function with invalid credentials
    user = login('user1', 'wrong_password', mock_mongo_client)

    # Assert that the user is None
    assert user is None

Step 4: Implement User Login Function
In the checkuser.py file under the app directory, implement your user login function:

from hashlib import sha256

def login(username, password, db_client):
    # Hash the provided password
    hashed_password = sha256(password.encode()).hexdigest()

    # Access the users collection from the mock MongoDB client
    users_collection = db_client['testdb']['users']

    # Search for the user by username and hashed password
    user = users_collection.find_one({'username': username, 'password': hashed_password})

    return user

Step 5: Run Tests
Run your tests using pytest:

pytest tests/

This will execute the test cases defined in test_checkuser.py using the mock MongoDB client provided by the mongomock library. Make sure your tests pass successfully.

Remember, this is a basic example to get you started. In a real-world scenario, you would likely have more comprehensive tests and handle additional cases.