Question 1

How to mock timers with Sinon in JavaScript tests?

Accepted Answer

Use `sinon.useFakeTimers()` to control setTimeout, Date, and other timers. You can advance time manually or set specific times, making it easy to test time-based logic without actual delays. Check the official documentation for code examples and best practices.

Question 2

What's the difference between Sinon spies, stubs, and mocks?

Accepted Answer

Spies record function calls and arguments without altering behavior; stubs replace functions to control returns or errors; mocks combine spies with pre-programmed expectations for verifying interactions. This allows precise control in unit tests, as detailed in the key features.

Question 3

Sinon vs Jest mocks: which should I use?

Accepted Answer

Sinon is framework-agnostic and comprehensive, ideal for projects not using Jest or needing advanced features like fake timers. Jest has built-in mocks but is tied to its ecosystem; choose Sinon for flexibility or Jest for an integrated solution.

Question 4

Can Sinon mock ES6 modules in Node.js?

Accepted Answer

Sinon can stub functions, but mocking ES6 modules often requires additional tooling like proxyquire or esmock due to module system limitations. For native ES modules, you might need to use workarounds or complementary libraries.

Question 5

How to integrate Sinon with Mocha or Jasmine testing frameworks?

Accepted Answer

Sinon works out of the box; just install and import it in your test files. For Mocha or Jasmine, use Sinon's spies and stubs directly in test cases without special configuration, as it doesn't pollute the global scope.

Question 6

Does Sinon support TypeScript?

Accepted Answer

Yes, Sinon has TypeScript definitions available via DefinitelyTyped (@types/sinon). However, ensure compatibility with your TypeScript version and be aware of potential type issues in complex mocking scenarios.

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