Full-Stack Development Quality Control & Assurance 4

Question 1

What does a 'spy' test double do differently from a 'stub'?

Accepted Answer

Spies record calls and arguments while optionally delegating to the real implementation; stubs just return preset values

Answer

A spy wraps the real function to record call metadata, whereas a stub replaces the function with a fixed-return implementation.

Question 2

In API testing, what does asserting the response schema validate?

Accepted Answer

That the response JSON structure and field types match the contract

Answer

Schema validation checks that response fields, types, and required properties match the API contract, catching breaking changes early.

Question 3

Which testing pyramid level is the MOST expensive to write, run, and maintain?

Accepted Answer

End-to-end (E2E) tests

Answer

E2E tests run through the full application stack in a real browser or environment, making them slowest and most brittle to maintain.

Question 4

What is 'contract testing' used for in a microservices architecture?

Accepted Answer

Ensuring provider services fulfill the API contracts that consumer services depend on

Answer

Contract testing (e.g., using Pact) verifies that a service's API fulfills the expectations recorded by its consumers, enabling independent deployments.

Question 5

When should you use `expect.assertions(n)` in a Jest async test?

Accepted Answer

To ensure a specific number of assertions ran, catching cases where async callbacks were never called

Answer

`expect.assertions(n)` prevents silent test passes when async callbacks are never invoked by requiring exactly n assertions to have been called.

Full-Stack Development Practice Test

Full-Stack Development Practice Test

Full-Stack Development Quality Control & Assurance 4