Jasmine.clock().install() Jest - Shell/Bash

Jasmine.clock().install() is a function provided by the Jasmine testing framework that enables mock clock functionality for your tests. This function is also available in the Jest testing framework.

Introduction

When writing tests that involve time-based logic, it can be difficult to test the code without waiting for real time to pass. This is where mock clocks come in handy. A mock clock is a feature that allows you to control the passage of time within your tests.

Jasmine.clock().install() installs a mock clock onto the global scope, which will increment itself with each call to setTimeout()/setInterval() and fire any callbacks scheduled for that time. This means that any time-based logic in your tests can be safely executed without the need to wait for actual time to pass.

Installation

Jasmine.clock().install() is already built into the Jasmine and Jest testing frameworks, so there is no need to install any additional dependencies.

Usage

To use Jasmine.clock().install(), simply call it at the beginning of your test suite or test case, before any code that relies on time-based logic is executed.

describe('my time-based logic', function() {
  beforeEach(function() {
    jasmine.clock().install();
  });

  afterEach(function() {
    jasmine.clock().uninstall();
  });

  it('should execute after a timeout of 1000ms', function() {
    var callback = jest.fn();
    setTimeout(callback, 1000);
    jasmine.clock().tick(1000);
    expect(callback).toHaveBeenCalled();
  });
});

In this example, we create a test suite for some time-based logic that involves a timeout of 1000ms. We install the mock clock before each test case, and uninstall it after each test case to ensure that it does not interfere with other tests.

We then create a callback function using Jest's mock function facility (jest.fn()), and schedule it to be executed after a timeout of 1000ms using setTimeout(). We then use jasmine.clock().tick(1000) to simulate the passage of 1000ms on the mock clock, which causes the callback function to be executed. Finally, we use the expect() function to ensure that the callback function has been called at least once.

Conclusion

Jasmine.clock().install() is a powerful tool that enables mock clock functionality in your tests, making it easier to test time-based logic without the need to wait for real time to pass. By using this function in your test suite or test cases, you can ensure that your tests execute quickly, reliably and consistently, even when testing complex time-based logic.