Testing with external services in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest test with mocked external API call

What is the output of this pytest test when the external API call is mocked to return status code 200?

PyTest

import requests
import pytest
from unittest.mock import patch

def fetch_data():
    response = requests.get('https://api.example.com/data')
    if response.status_code == 200:
        return response.json()
    return None

@patch('requests.get')
def test_fetch_data(mock_get):
    mock_get.return_value.status_code = 200
    mock_get.return_value.json = lambda: {'key': 'value'}
    result = fetch_data()
    assert result == {'key': 'value'}
    print('Test passed')

A Test passed

B TypeError

C AssertionError

D No output

💡 Hint

Consider what the mock object returns for status_code and json method.

The mock replaces requests.get to return a response with status_code 200 and a json method returning {'key': 'value'}. The assertion passes and 'Test passed' is printed.

❓ assertion

intermediate

Correct assertion for API response content

Which assertion correctly verifies that the API response contains a 'user' key with a non-empty dictionary?

PyTest

response = {'user': {'id': 1, 'name': 'Alice'}}

A assert 'user' in response and isinstance(response['user'], dict) and response['user']

B assert response['user'] != None

C assert response['user'] is not None and len(response['user']) > 0

D assert response.get('user') == {}

💡 Hint

Check for key existence, type, and non-empty dictionary.

Option A checks that 'user' key exists, is a dictionary, and is not empty. Option A only checks not None but could be empty. Option A is valid but less explicit about type. Option A asserts empty dict which is incorrect.

🔧 Debug

advanced

Identify the cause of test failure with external service timeout

Given this pytest test, why does it fail with a TimeoutError?

PyTest

import requests
import pytest

def get_data():
    return requests.get('https://slow.api.example.com/data', timeout=1).json()

def test_get_data():
    data = get_data()
    assert 'result' in data

A The requests.get call is missing required headers causing a connection error

B The external API is too slow and exceeds the 1 second timeout causing TimeoutError

C The test assertion is incorrect and causes AssertionError

D The function get_data returns None causing TypeError

💡 Hint

Consider the timeout parameter in requests.get and the error type.

The test fails because the external API response takes longer than 1 second, triggering a TimeoutError before the assertion.

❓ framework

advanced

Best pytest fixture scope for external service setup

Which pytest fixture scope is best to minimize external service setup overhead when running multiple tests that share the same service state?

A module - runs setup once per module

B function - runs setup before each test function

C session - runs setup once per test session

D class - runs setup once per test class

💡 Hint

Think about how often you want to initialize the external service for all tests.

Session scope runs once for the entire test session, minimizing repeated setup for external services shared across tests.

🧠 Conceptual

expert

Handling flaky tests caused by external service instability

Which strategy is most effective to handle flaky tests caused by intermittent failures of an external service?

A Run the tests only manually when needed

B Ignore the flaky tests to avoid blocking the pipeline

C Increase the test timeout indefinitely to wait for the service

D Use test retries with exponential backoff and mock the external service in CI

💡 Hint

Consider reliability and automation best practices.

Retries with backoff help handle transient failures, and mocking in CI ensures tests are stable and fast. Ignoring or manual runs reduce test coverage and automation benefits.