Testing with external services in PyTest - Build an Automation Script

Verify user data retrieval from external API

Preconditions (2)

Step 1: Send a GET request to https://api.example.com/users/123

Step 2: Receive the JSON response containing user details

Step 3: Verify the response status code is 200

Step 4: Verify the response JSON contains 'id' equal to 123

Step 5: Verify the response JSON contains 'name' and 'email' fields

✅ Expected Result: The API returns status 200 and JSON with correct user id, name, and email fields

Automation Requirements - pytest

Assertions Needed:

Response status code is 200

Response JSON 'id' equals 123

Response JSON contains 'name' key

Response JSON contains 'email' key

Best Practices:

Use requests library to call external API

Use pytest fixtures for setup if needed

Handle possible connection errors gracefully

Avoid hardcoding URLs by using constants

Keep tests independent and repeatable

Automated Solution

PyTest

import requests
import pytest

API_URL = "https://api.example.com/users/123"

@pytest.fixture

def get_user_data():
    try:
        response = requests.get(API_URL, timeout=5)
        response.raise_for_status()
        return response
    except requests.RequestException as e:
        pytest.skip(f"Skipping test due to connection error: {e}")


def test_user_data_retrieval(get_user_data):
    response = get_user_data
    assert response.status_code == 200, f"Expected status 200 but got {response.status_code}"
    data = response.json()
    assert data.get('id') == 123, f"Expected user id 123 but got {data.get('id')}"
    assert 'name' in data, "Response JSON missing 'name' field"
    assert 'email' in data, "Response JSON missing 'email' field"

The code uses requests to call the external API URL defined as a constant API_URL. A pytest fixture get_user_data handles the GET request and skips the test if the API is unreachable or returns an error.

The test function test_user_data_retrieval uses this fixture to get the response, then asserts the status code is 200. It parses the JSON and checks the id is 123 and that name and email keys exist. This keeps the test clear, independent, and handles external service issues gracefully.

Common Mistakes - 4 Pitfalls

Hardcoding the API URL inside the test function

Not handling connection errors or timeouts

Not checking the response status code before parsing JSON

Using print statements instead of assertions

Bonus Challenge

Now add data-driven testing with 3 different user IDs: 123, 456, and 789

Show Hint