CODEWITHSUNDEEP
javascriptjestjs
JSK
JSK

Reputation: 1276

Alternative to spyOn().and.callfake in Jestjs

I used to have spyOn().and.callFake in jasmine and it helps a lot in my tests, now I'm using Jest, I've found in the doc that jest.spyOn() exist but without the callFake.

My Question: How to spy on a method and call Fake with Jest and expect?

Upvotes: 20

Views: 17537

Answers (1)

eddyP23
eddyP23

Reputation: 6825

jest.spyOn official documentation gives a great answer:

Note: By default, jest.spyOn also calls the spied method. This is different behavior from most other test libraries. If you want to overwrite the original function, you can use jest.spyOn(object, methodName).mockImplementation(() => customImplementation) or object[methodName] = jest.fn(() => customImplementation);

So in your case just pass a fake method to customImplementation.

Upvotes: 22

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