test setTimeout use-case

devrelm · Aug 23, 2016 · 85e2683 · 85e2683
1 parent 6790537
commit 85e2683
Showing 1 changed file with 178 additions and 0 deletions.
diff --git a/tests/setTimeout.tests.js b/tests/setTimeout.tests.js
@@ -0,0 +1,178 @@
+const jsdom = require('jsdom').jsdom;
+const sinon = require('sinon');
+const test = require('./helpers').test;
+
+const FRAME_TIME = 1000/60;
+const frameTick = () => {
+    clock.tick(FRAME_TIME);
+};
+
+const setup = () => {
+    const document = jsdom('<html><body></body></html>');
+    global.window = document.defaultView;
+    global.clock = sinon.useFakeTimers();
+    sinon.stub(window, 'setTimeout', global.setTimeout);
+    global.setTimeout = window.setTimeout;
+};
+const teardown = () => {
+    global.window.setTimeout.restore();
+    global.clock.restore();
+};
+
+test('calls setTimeout once for multiple event occurrences', (t) => {
+    t.plan(3);
+    setup();
+
+    const throttle = require('../throttle');
+    const throttledListener = throttle(() => {});
+    const event = 'resize';
+
+    window.addEventListener(event, throttledListener);
+
+    t.equal(window.setTimeout.callCount, 0,
+        'sanity check - setTimeout not called before event dispatch');
+
+    window.dispatchEvent(new window.Event(event));
+
+    t.equal(window.setTimeout.callCount, 1,
+        'calls setTimeout upon first event dispatch');
+
+    window.dispatchEvent(new window.Event(event));
+
+    t.equal(window.setTimeout.callCount, 1,
+        'does not call setTimeout again upon second event dispatch');
+}, teardown);
+
+test('waits 1/60th of a second to call the callback', (t) => {
+    setup();
+    t.plan(4);
+
+    const throttle = require('../throttle');
+    const listener = sinon.spy();
+    const throttledListener = throttle(listener);
+    const event = 'resize';
+
+    window.addEventListener(event, throttledListener);
+
+    t.equal(listener.callCount, 0,
+        'sanity check - listener not called before event dispatch');
+
+    window.dispatchEvent(new window.Event(event));
+
+    t.equal(listener.callCount, 1,
+        'calls listener upon first event dispatch');
+
+    listener.reset();
+    window.dispatchEvent(new window.Event(event));
+    clock.tick(FRAME_TIME - 1);
+    window.dispatchEvent(new window.Event(event));
+
+    t.equal(listener.callCount, 0,
+        'does not call the listener again before 1/60th of a second');
+
+    clock.tick(1);
+
+    t.equal(listener.callCount, 0,
+        'events fired prior to 1/60th sec do not set callbacks for after 1/60th sec');
+}, teardown);
+
+test('calls the listener multiple times for multiple event/frame cycles', (t) => {
+    setup();
+    t.plan(3);
+
+    const throttle = require('../throttle');
+    const listener = sinon.spy();
+    const throttledListener = throttle(listener);
+    const event = 'resize';
+
+    window.addEventListener(event, throttledListener);
+
+    t.equal(listener.callCount, 0,
+        'sanity check - listener not called before event dispatch');
+
+    window.dispatchEvent(new window.Event(event));
+    frameTick();
+
+    t.equals(listener.callCount, 1,
+        'listener is called during first event/frame cycle');
+
+    window.dispatchEvent(new window.Event(event));
+    frameTick();
+
+    t.equals(listener.callCount, 2,
+        'listener is called during second event/frame cycle');
+}, teardown);
+
+test('calls the listener once per event dispatch', (t) => {
+    setup();
+    t.plan(3);
+
+    const throttle = require('../throttle');
+    const listener = sinon.spy();
+    const throttledListener = throttle(listener);
+    const event = 'resize';
+
+    window.addEventListener(event, throttledListener);
+
+    t.equal(listener.callCount, 0,
+        'sanity check - listener not called before event dispatch');
+
+    window.dispatchEvent(new window.Event(event));
+    frameTick();
+
+    t.equal(listener.callCount, 1,
+        'listener is called during first event/frame cycle');
+
+    frameTick();
+
+    t.equal(listener.callCount, 1,
+        'listener is not called during second frame without event');
+}, teardown);
+
+test('no longer calls listener after removeEventListener', (t) => {
+    setup();
+    t.plan(2);
+
+    const throttle = require('../throttle');
+    const listener = sinon.spy();
+    const throttledListener = throttle(listener);
+    const event = 'resize';
+
+    window.addEventListener(event, throttledListener);
+
+    window.dispatchEvent(new window.Event(event));
+    frameTick();
+
+    t.equal(listener.callCount, 1,
+        'sanity check - listener called during first event/frame cycle');
+
+    window.removeEventListener(event, throttledListener);
+
+    window.dispatchEvent(new window.Event(event));
+    frameTick();
+
+    t.equal(listener.callCount, 1,
+        'listener is not called during second cycle after throttled listener is removed');
+}, teardown);
+
+test('passes the event object to the original listener', (t) => {
+    setup();
+    t.plan(2);
+
+    const throttle = require('../throttle');
+    const listener = sinon.spy();
+    const throttledListener = throttle(listener);
+    const event = 'resize';
+    const eventObject = new window.Event(event);
+
+    window.addEventListener(event, throttledListener);
+
+    window.dispatchEvent(eventObject);
+    frameTick();
+
+    t.equal(listener.callCount, 1,
+        'sanity check - listener called during first event/frame cycle');
+
+    t.equal(listener.getCall(0).args[0], eventObject,
+        'listener called with the provided event object');
+}, teardown);