gecko-dev/testing/modules/TestUtils.jsm

88 строки
2.9 KiB
JavaScript

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* This module implements a number of utilities useful for testing.
*
* Additions to this module should be generic and useful to testing multiple
* features. Utilities only useful to a sepcific testing framework should live
* in a module specific to that framework, such as BrowserTestUtils.jsm in the
* case of mochitest-browser-chrome.
*/
"use strict";
this.EXPORTED_SYMBOLS = [
"TestUtils",
];
const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/Services.jsm");
this.TestUtils = {
executeSoon(callbackFn) {
Services.tm.dispatchToMainThread(callbackFn);
},
/**
* Waits for the specified topic to be observed.
*
* @param {string} topic
* The topic to observe.
* @param {function} checkFn [optional]
* Called with (subject, data) as arguments, should return true if the
* notification is the expected one, or false if it should be ignored
* and listening should continue. If not specified, the first
* notification for the specified topic resolves the returned promise.
*
* @note Because this function is intended for testing, any error in checkFn
* will cause the returned promise to be rejected instead of waiting for
* the next notification, since this is probably a bug in the test.
*
* @return {Promise}
* @resolves The array [subject, data] from the observed notification.
*/
topicObserved(topic, checkFn) {
return new Promise((resolve, reject) => {
Services.obs.addObserver(function observer(subject, topic, data) {
try {
if (checkFn && !checkFn(subject, data)) {
return;
}
Services.obs.removeObserver(observer, topic);
resolve([subject, data]);
} catch (ex) {
Services.obs.removeObserver(observer, topic);
reject(ex);
}
}, topic);
});
},
/**
* Takes a screenshot of an area and returns it as a data URL.
*
* @param eltOrRect
* The DOM node or rect ({left, top, width, height}) to screenshot.
* @param win
* The current window.
*/
screenshotArea(eltOrRect, win) {
if (eltOrRect instanceof Ci.nsIDOMElement) {
eltOrRect = eltOrRect.getBoundingClientRect();
}
let { left, top, width, height } = eltOrRect;
let canvas = win.document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
let ctx = canvas.getContext("2d");
let ratio = win.devicePixelRatio;
canvas.width = width * ratio;
canvas.height = height * ratio;
ctx.scale(ratio, ratio);
ctx.drawWindow(win, left, top, width, height, "#fff");
return canvas.toDataURL();
}
};