RxJS test with marble iagrams

with-marbles.ts

it('multiplies each number by 2', () => {
  createScheduler().run(({ cold, expectObservable }) => {
    const values = { a: 1, b: 2, c: 3, x: 2, y: 4, z: 6 }

    const numbers$ = cold('a-b-c-|', values) as Observable<number>
    const resultDiagram = 'x-y-z-|'

    expectObservable(numTwoTimes(numbers$)).toBe(resultDiagram, values)
  })
})