Christian Droulers

Testing the current date with JavaScript

Posted on 2015-03-19

When you have time-sensitive operations that require using the current date, it’s always a mess to test.

With JavaScript, the easiest way to get the current date is simply new Date() or new Date(Date.now()). But if we start using that everywhere, when we get to a point where we want to test operations that lookup the current date, we become a bit stuck. Since our test data would be static, but not the current date.

Therefore, in our application, we simply created a global method called getCurrentDate which, by default, returns new Date().

In our JavaScript tests, we can override the method in the beforeEach setup of the test.

beforeEach(() => {
    window.getCurrentDate = () => {
        return new Date("2015-03-19");
    };
});

With that, our current date is always what we want in tests. We’ve also used it in our Selenium tests to ensure our UI thinks it’s the date we want.

((IJavaScriptExecutor)SeleniumDriver).ExecuteScript(
    string.Format(@"app.GetCurrentDate = function() {{
        return new Date(new Date('{0}').setMinutes(new Date().getTimezoneOffset() + 60));
    }}", p0));

It requires making changes to an existing app if you are already using new Date() everywhere. It’s a small cost to pay for testability!