TotT: JavaScript: Simulating Time in jsUnit Tests
Thursday, March 29, 2007
Sometimes you need to test client-side JavaScript code that uses
setTimeout() to do some work in the future. jsUnit contains the Clock.tick() method, which simulates time passing without causing the test to sleep. For example, this function will set up some callbacks to update a status message over the course of four seconds ...Read More
Sometimes you need to test client-side JavaScript code that uses
The jsUnit test for this function would look like this:
This test will run very quickly - it does not require four seconds to run.
setTimeout() to do some work in the future. jsUnit contains the Clock.tick() method, which simulates time passing without causing the test to sleep. For example, this function will set up some callbacks to update a status message over the course of four seconds:
function showProgress(status) {
status.message = "Loading";
for (var time = 1000; time <= 3000; time += 1000) {
// Append a '.' to the message every second for 3 secs.
setTimeout(function() {
status.message += ".";
}, time);
}
setTimeout(function() {
// Special case for the 4th second.
status.message = "Done";
}, 4000);
}
The jsUnit test for this function would look like this:
function testUpdatesStatusMessageOverFourSeconds() {
Clock.reset(); // Clear any existing timeout functions on the event queue.
var status = {};
showProgress(status); // Call our function.
assertEquals("Loading", status.message);
Clock.tick(2000); // Call any functions on the event queue that have
// been scheduled for the first two seconds.
assertEquals("Loading..", status.message);
Clock.tick(2000); // Same thing again, for the next two seconds.
assertEquals("Done", status.message);
}
This test will run very quickly - it does not require four seconds to run.
Clock supports the functions setTimeout(),setInterval(), clearTimeout(), andclearInterval(). The Clock object is defined injsUnitMockTimeout.js, which is in the same directory asjsUnitCore.js.
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