packages/utils/throttle.test.ts

   1 import throttle from './throttle';
   2
   3 describe('throttle()', () => {
   4     beforeAll(() => {
   5         jest.useFakeTimers();
   6     });
   7
   8     afterEach(() => {
   9         jest.clearAllTimers();
  10     });
  11
  12     afterAll(() => {
  13         jest.useRealTimers();
  14     });
  15
  16     it('invokes function at most once every wait milliseconds', () => {
  17         const functionToThrottle = jest.fn();
  18         const wait = 1000;
  19         const throttledFunction = throttle(functionToThrottle, wait);
  20
  21         throttledFunction();
  22         expect(functionToThrottle).toHaveBeenCalledTimes(1);
  23
  24         // Call function just before the wait time expires
  25         jest.advanceTimersByTime(wait - 1);
  26         throttledFunction();
  27         expect(functionToThrottle).toHaveBeenCalledTimes(1);
  28
  29         // fast-forward until 1st call should be executed
  30         jest.advanceTimersByTime(1);
  31         expect(functionToThrottle).toHaveBeenCalledTimes(2);
  32
  33         throttledFunction();
  34         expect(functionToThrottle).toHaveBeenCalledTimes(2);
  35
  36         jest.advanceTimersByTime(wait);
  37         expect(functionToThrottle).toHaveBeenCalledTimes(3);
  38     });
  39 });