HugoDF / jest-mock-date-examples

Different approaches to mocking the Date in Jest tests

Jest Mock Date examples

Different approaches to mocking the Date in Jest tests

See the full post and explanation at codewithhugo.com/mocking-the-current-date-in-jest-tests.

There are 2 general approaches to mocking the current date:

• Using new Date() and mocking the constructor.
• Using new Date(Date.now()) and mocking the output of Date.now().

For each of those approaches in the application code, this repo has examples for a spy-based approach and a full function/constructor stub/mock replacement:

• Date.now() + full mock/stub: see ./src/stub-date-now.test.js
• Date.now() + spy: see ./src/spy-date-now.test.js
• new Date() + full mock/stub: see ./src/stub-date-class.test.js
• new Date() + spy: see ./src/spy-new-date.test.js

Running the tests

Packages were installed with yarn, although npm should work just as well.

• Run yarn
• Run yarn test