Learning Redux

.mock property

All mock functions have a special .mock property, which stores data about how the function has been called:

const getUser = jest.fn()getUser('dan')getUser('des')console.log(getUser.mock.calls)

The preceding example would print the following output:

[ ['dan'], ['des'] ]

The .mock property also keeps track of the value of this for each call:

const mockTest = jest.fn()const a = new mockTest()const b = {}const bound = mockTest.bind(b)bound()console.log(mockTest.mock.instances)

The preceding example would print an array with the context a and the context b, like this: [ <a>, <b> ].