Jest documentation expect (screen. That said, jest is an excellent unit testing option which provides great TypeScript support. Note: We assume you start off with a simple node package.json setup. This is true for stub/spy assertions like .toBeCalled(), .toHaveBeenCalled(). It’s possible to require/import and expose the real module while using jest.mock. import Enzyme from 'enzyme' import Adapter from 'enzyme-adapter-react-16' Enzyme.configure({ adapter: new Adapter() }) package.json "jest": { "setupFiles": [ "test/setup.js" ] } This configures Enzyme for React v16, and Jest to automatically configure Enzyme for you. Jest expect has a chainable .not assertion which negates any following assertion. jest.requireActual(moduleName) Returns the actual module instead of a mock, bypassing all checks on whether the module should receive a mock implementation or not. spyOn ( mathjs , 'log' ) const result = mathjs . In cases 2 and 3, we use queryByTestId instead of getByTestId.queryByTestId doesn't fail when the queried element doesn't exist, instead, it returns either a value or null and that's what we test with expect().toBeTruthy() and expect().toBeNull(). I feel like this is such a simple […] As a bonus, Jest not only can unit test Reactive Native apps, but it can also unit test other JavaScript frameworks, such as Angular, Vue, Bable, TypeScript, and Node. Pastebin.com is the number one paste tool since 2002. When you import a package, you can tell Jest to “spy” on the execution of a particular function, using spyOn(), without affecting how that method works. Jest is built into React, which makes Jest a simple, out-of-the-box solution to for React Native unit testing. expect (screen. With Jasmine this is super easy — The application code: And the test code: What’s the equivalent with Jest? Jest is the best option for most React Native projects. getByTestId ('location-display')). toHaveTextContent (route) Reducing boilerplate # You can use the wrapper option to wrap a MemoryRouter around the component you want to … This is seen as good practice at the unit test level, as we don’t want these tests dependant on an external API which will … Using Enzyme with Mocha. toHaveTextContent ('My Name Is: C3P0') * To test a component that provides a context value, render a matching * consumer as the child expect-enzyme for expect. Example: const mathjs = require ( 'mathjs' ) test ( `The mathjs log function` , () => { const spy = jest . Between test runs we need mocked/spied on imports and functions to be reset so that assertions don’t fail due to stale calls (from a … Using Enzyme with SystemJS. should-enzyme for should.js. Using Enzyme with Browserify. There are other adapters in Enzyme’s installation instructions. jest-enzyme with Jest. 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