var UpdateQueue = require('../update_queue'); describe('UpdateQueue', function() { it('executes task immediately if there are no pending tasks', function(done) { const q = new UpdateQueue(); var updated = false; const updateFn = function(a, b, cb) { expect(a).toEqual(1); expect(b).toEqual(2); updated = true; cb(); }; q.enqueue(updateFn, [1, 2], function() { expect(updated).toEqual(true); done(); }); }); it('serializes async tasks in the order submitted', function(done) { const q = new UpdateQueue(); var progress = []; // This simulates a condition in which events are being received asynchronously and each // event triggers an asynchronous task. We want to make sure that the tasks are executed in // the order submitted, even if one is submitted during the execution of the previous one. const taskFn = function(i, cb) { progress.push('start ' + i); // assume that we're doing something asynchronous here - make sure it takes a little time setTimeout(cb, 20); }; const expected = [ 'submit 1', 'start 1', // note, this one executes immediately because there was nothing pending 'submit 2', 'submit 3', 'end 1', 'start 2', 'end 2', 'start 3', 'end 3' ]; for (var i = 1; i <= 3; i++) { const j = i; setImmediate(function() { progress.push('submit ' + j); q.enqueue(taskFn, [j], function() { progress.push('end ' + j); if (j >= 3) { expect(progress).toEqual(expected); done(); } }); }); } }); });