It returns true if there has been any one call with the matching argument(s). It leads to massive tests rewriting in case of code refactoring The better solution is to test component as a black box. A quick overview to Jest, a test framework for Node.js. Use Jest’s clearMocks configuration setting to ensure your spies are cleared before each test. Even if you're not using the module that needs mocking in your test, you'll need to import or require it so that Jest can mock it's reference before the file you're trying to test brings it in. This guide targets Jest v20. expect(requests.ApiVersions.protocol).not. It seems that nowadays not many nodeJS projects are tested with unit tests and are instead tested with an approach more forward to integration or funcional testing. This is true for stub/spy assertions like .toBeCalled(), .toHaveBeenCalled(). Although Jest will always append a number at the end of a snapshot name, short descriptive hints may be more useful than numbers in differentiating multiple snapshots in a single it or test block. available in Jest 19.0.0+ # expect.stringContaining(string) matches any received string that contains the exact expected string. In the spec below, the circumference() method is called upon by passing the argument 2. That's it for creating a Jest mock for Axios by going through one example. A few more thoughts: If you want to mock a post instead of a get request for Axios, just apply the mockImplementationOnce() for … For example, let's say you have a drinkEach (drink, Array) function that takes a drink function and applies it to array of passed beverages. c) Now add a snapshot test. Given that, I think we're unlikely to change this behavior. A great way to do this is using the test.each function to avoid duplicating code. The toHaveBeenCalledWith() matcher verifies whether the spied method has been called with the right argument(s). The actual object is much larger but we don’t really care about the other properties, in this case the user information is the moving parts in the object. Enzyme was created by AirBnB to render components for testing. fs-extra contains methods that aren't included in the vanilla Node.js fs package. In our example, we are using semantic form markup using the