Jasmine has a very complicated way of testing
setTimeout
and
setInterval
that I, frankly, don't understand very well. To add to the complication, my code is server-side, so I can't just
spyOn( window, 'setInterval' )
. Jasmine also gives a poor example with trivial code--not code someone (like myself) would actually be testing if they actually needed to refer to the docs.
This needs testing. Node.js docs explain really well that setInterval is not on the window, it's on a globals object:
In browsers, the top-level scope is the global scope. That means that in browsers if you're in the global scope var something will define a global variable. In Node.js this is different. The top-level scope is not the global scope; var something inside an Node.js module will be local to that module.
Test Me
tl;dr:
// require the function you're testing
var updateEveryMinute = require( './intervals' ).updateEveryMinute;
// require the function called by setInterval.
var update = require( './update' ).update
describe('updateEveryMinute', function() {
var intervalId;
afterEach(function() {
clearInterval( intervalId );
it('should be defined as a function', function() {
expect( typeof updateEveryMinute ).toBe( 'function' );
it('should set an interval to run update every minute', function() {
spyOn( global, 'setInterval' ).andCallThrough();
intervalId = updateEveryMinute();
expect( global.setInterval ).toHaveBeenCalled();
expect( global.setInterval ).toHaveBeenCalledWith( update, 60000 );
it('should return an interval id', function() {
spyOn( global, 'setInterval' ).andCallThrough();
intervalId = updateEveryMinute();
expect( intervalId ).toBeDefined();
expect( typeof intervalId ).toBe( 'object' );
The Breakdown
// see this in each test
intervalId = updateEveryMinute();
afterEach(function() {
clearInterval( intervalId );
setInterval and setTimeout return information when created so you can clear them later. After each invocation of the tested function, I need to clear the interval so it doesn't actually call the update function.
spyOn( global, 'setInterval' ).andCallThrough();
Since there is no window in Node.js, we'll create a spy on the global object. And, sure, let's call the real thing using andCallThrough(); no need to mock here!
We expect setInterval to have been called, because that's basically all our function does.
See that second test, though? It's jucy!
I required the same function (update) in the test spec that I pass to the real function, so I can make a very real comparison without having to replicate all of the code for update. This won't save you time if you've passed setInterval an anonymous function--you'll just have to retype it.
