Mocking database calls in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is mocking in the context of database calls?

Mocking means creating fake versions of database calls to test code without using a real database. It helps check if the code works correctly and quickly.

beginner

Why do we mock database calls in Express apps?

We mock database calls to avoid slow or unreliable real database access during tests. It makes tests faster and safer by isolating the code from the database.

intermediate

Which tool can you use to mock functions in Express tests?

You can use libraries like Sinon.js or Jest to create mocks and spies for database functions in Express tests.

intermediate

How does mocking help when testing error handling in database calls?

Mocking lets you simulate errors from the database, so you can check if your code handles those errors properly without needing a real database failure.

intermediate

What is a stub in mocking database calls?

A stub is a fake function that replaces a real database call and returns preset data or errors to control test scenarios.

What is the main benefit of mocking database calls in Express tests?

A Connects to multiple databases

B Improves database performance

C Automatically fixes database errors

D Faster and isolated tests without real database

Mocking helps tests run faster and isolates code from the real database.

Which library is commonly used to mock functions in JavaScript tests?

A Express

B React

C Sinon.js

D MongoDB

Sinon.js is a popular library for mocking and spying on functions.

What does a stub do in mocking?

A Replaces a function with preset responses

B Deletes the database

C Runs the real database query

D Creates a new database

A stub replaces a real function to return controlled data for tests.

How can mocking help test error handling?

A By ignoring errors

B By simulating database errors

C By fixing errors automatically

D By connecting to a backup database

Mocking can simulate errors so you can check how your code reacts.

When should you avoid mocking database calls?

A When you want to test real database integration

B When writing unit tests

C When testing error handling

D When running fast tests

Mocking is not used when you want to test actual database behavior.

Explain how mocking database calls improves testing in Express applications.

Think about speed and control in tests.

Describe the difference between a mock and a stub when testing database calls.

Focus on purpose and behavior tracking.