Run Jest tests

Run tests in watch mode

Group related tests together

jest/expect

Make assertions in tests

jest

expect

assertions

expect(value).toBe(expected)

expect is used to make assertions about values in your tests with various matchers.

Exact equality

expect(result).toBe(42)

Array contains item

expect(array).toContain(item)

Function was called

expect(fn).toHaveBeenCalled()

Write individual test cases

Mock timers in tests

Debug failing tests