React Native template project with Jest tests

Trying out how to use Jest with React Native.

There are two components, each with a test:

Button: A very simple component with no state, the test is trivial.

CreateScreen: A stateful component that expands a part of the UI on tap. The question here is what should be the right API for simulating the tap in the test. The component uses React Native's <TouchableOpacity onPress={this._onHelpPress}>. The onPress callback is not present in the "native" snapshot rendered by Jest, because TouchableOpacity works by attaching some native events to its child. The names of those events are an implementation detail we should not be relying on in the test.

Running tests

Simply do:

$ cd AppWithJest2
$ npm test
2 tests passed

Iterating on your code

When changing a component, run tests again using npm test.

If tests failed you either found a bug (yay!) or this change in the rendered tree is expected: run npm test -- -u.