@hirez_io/observer-spy

@hirez_io/observer-spy 👀💪

A simple little class that helps making Observable testing a breeze

What's the problem?

Testing RxJS observables is usually hard, especially when testing advanced use cases.

This library:

✅ Easy to understand

✅ Reduces the complexity

✅ Makes testing advanced observables easy

Installation

yarn add -D @hirez_io/observer-spy

or

npm install -D @hirez_io/observer-spy

Usage

new ObserverSpy()

In order to test observables, you can use an ObserverSpy instance to "record" all the messages a source observable emits and to get them as an array.

You can also spy on the error or complete states of the observer.

Example:

it('should spy on Observable values', () => {
  const observerSpy = new ObserverSpy();
  const fakeValues = ['first', 'second', 'third'];
  const fakeObservable = of(...fakeValues);

  const subscription = fakeObservable.subscribe(observerSpy);

  // DO SOME LOGIC HERE

  // unsubscribing is optional, it's good for stopping intervals etc
  subscription.unsubscribe();

  expect(observerSpy.receivedNext()).toBe(true);

  expect(observerSpy.getValues()).toEqual(fakeValues);

  expect(observerSpy.getValuesLength()).toEqual(3);

  expect(observerSpy.getFirstValue()).toEqual('first');

  expect(observerSpy.getValueAt(1)).toEqual('second');

  expect(observerSpy.getLastValue()).toEqual('third');

  expect(observerSpy.receivedComplete()).toBe(true);
});

it('should spy on Observable errors', () => {
  const observerSpy = new ObserverSpy();

  const fakeObservable = throwError('FAKE ERROR');

  fakeObservable.subscribe(observerSpy);

  expect(observerSpy.receivedError()).toBe(true);

  expect(observerSpy.getError()).toEqual('FAKE ERROR');
});