Solution - Test Custom Operator

import { TestScheduler } from 'rxjs/testing';

import { verifyPasscode } from './verify-password.operator';

const BOOLEANS = {
  T: true,
  F: false
};

describe('custom operators', () => {
  let testScheduler: TestScheduler;

  beforeEach(() => {
    testScheduler = new TestScheduler((actual, expected) =>
      expect(actual).toEqual(expected)
    );
  });

  test('verify passcode passes', () => {
    testScheduler.run(({ cold, expectObservable }) => {
      const values = {
        a: 1
      };
      const PASSCODE = [1, 1, 1, 1];
      const source = cold('-a-a-a-a', values);
      const expected = '   -------T';
      expectObservable(source.pipe(verifyPasscode(PASSCODE))).toBe(
        expected,
        BOOLEANS
      );
    });
  });

  test('verify password never emits', () => {
    testScheduler.run(({ cold, expectObservable }) => {
      const values = {
        a: 1
      };
      const PASSCODE = [1, 1, 1, 1];
      const source = cold('-a', values);
      const expected = '   --';
      expectObservable(source.pipe(verifyPasscode(PASSCODE))).toBe(
        expected,
        BOOLEANS
      );
    });
  });

  test('verify passcode fails after 4 incorrect values', () => {
    testScheduler.run(({ cold, expectObservable }) => {
      const values = {
        a: 1,
        b: 2
      };
      const PASSCODE = [1, 1, 1, 1];
      const source = cold('-b-b-c-d', values);
      const expected = '   -------F';
      expectObservable(source.pipe(verifyPasscode(PASSCODE))).toBe(
        expected,
        BOOLEANS
      );
    });
  });

  test('verify passcode fails twice after 8 incorrect values', () => {
    testScheduler.run(({ cold, expectObservable }) => {
      const values = {
        a: 1,
        b: 2
      };
      const PASSCODE = [1, 1, 1, 1];
      const source = cold('-b-b-c-d-a-b-a-a', values);
      const expected = '   -------F-------F';
      expectObservable(source.pipe(verifyPasscode(PASSCODE))).toBe(
        expected,
        BOOLEANS
      );
    });
  });
});