@variantjs/core/src/__tests__/debounce.test.ts

VariantJS common functions and utilities

import debounce from '../helpers/debounce';

describe('debounce', () => {
  it('runs the function after the default time', () => {
    const mockFn = jest.fn();

    jest.useFakeTimers();

    debounce(mockFn)();

    expect(mockFn).not.toHaveBeenCalled();

    jest.advanceTimersByTime(199);

    expect(mockFn).not.toHaveBeenCalled();

    jest.advanceTimersByTime(1);

    expect(mockFn).toHaveBeenCalled();
  });

  it('reset the time if function called again', () => {
    const mockFn = jest.fn();

    jest.useFakeTimers();

    const func = debounce(mockFn, 200);

    func();

    expect(mockFn).not.toHaveBeenCalled();

    jest.advanceTimersByTime(199);

    func();

    jest.advanceTimersByTime(199);

    expect(mockFn).not.toHaveBeenCalled();

    jest.advanceTimersByTime(1);

    expect(mockFn).toHaveBeenCalled();
  });

  it('can cancel the call', () => {
    const mockFn = jest.fn();

    jest.useFakeTimers();

    const func = debounce(mockFn, 200);

    func();

    func.cancel();

    jest.advanceTimersByTime(300);

    expect(mockFn).not.toHaveBeenCalled();
  });

  it('handle the function params ', () => {
    const mockFn = jest.fn();

    jest.useFakeTimers();

    debounce(mockFn, 100)('test', 1);

    jest.advanceTimersByTime(100);

    expect(mockFn).toHaveBeenLastCalledWith(['test', 1]);
  });

  it('runs the function inmediatly if wait is falsy value', () => {
    const mockFn = jest.fn();

    debounce(mockFn, 0)();

    expect(mockFn).toHaveBeenCalled();
  });
});