Testing with external services in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main challenge when testing code that interacts with external services?

The main challenge is that external services can be unreliable, slow, or change unexpectedly, which can cause tests to fail even if the code is correct.

beginner

Why do we use mocking in tests involving external services?

Mocking replaces the real external service with a fake one that returns controlled responses, making tests faster, reliable, and independent of the real service.

intermediate

What pytest feature helps to replace parts of your system during tests?

Pytest supports fixtures and the 'monkeypatch' fixture to replace functions or objects temporarily during a test.

intermediate

How can you simulate different responses from an external API in pytest?

You can create a mock function that returns different data or raises exceptions, then use monkeypatch to replace the real API call with this mock during tests.

advanced

What is a good practice to ensure tests with external services remain fast and reliable?

Use mocking or stubbing to avoid real network calls, and test integration with real services separately in dedicated integration tests.

Why should tests avoid calling real external services directly?

A Because real services always return errors

B Because real services can be slow or unavailable, causing flaky tests

C Because tests must always run offline

D Because external services are illegal to use in tests

Real external services can be slow, unreliable, or change unexpectedly, which makes tests flaky and slow.

What does mocking an external service mean in testing?

A Replacing the real service with a fake one that returns controlled data

B Deleting the external service

C Running the external service on your local machine

D Ignoring the external service calls

Mocking means replacing the real service with a fake version that returns predictable responses for testing.

Which pytest feature helps you replace functions or objects during a test?

A parametrize decorator

B assert statement

C monkeypatch fixture

D skip marker

The monkeypatch fixture allows you to replace or modify objects temporarily during a test.

What is a benefit of using mocking in tests with external services?

A Tests run faster and are more reliable

B Tests become more complex

C Tests require internet connection

D Tests always fail

Mocking avoids real network calls, making tests faster and less likely to fail due to external issues.

When should you test with the real external service instead of mocking?

A Only when the service is down

B Never, mocking is always better

C Only for unit tests

D In dedicated integration tests to verify real interactions

Integration tests check real interactions with external services to ensure everything works end-to-end.

Explain why mocking external services is important in automated tests.

Think about what happens if your test depends on the internet or a service that might be down.

Describe how you would use pytest to mock an external API call in a test.

Focus on how pytest's monkeypatch can help replace parts of your code during tests.