Unit Testing

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学习本教程你将需要安装SDK, 学习 基本操作cfx,和学习过编写可重复模块(writing reusable modules).

如果你在使用 jpm 而不是 cfx, 请看关于cfx, 而且重点看加载测试模块(loading modules from test code).

SDK提供了一个框架,为你的代码创建和运行单元测试.接下来我们将演示如何写一个关于Base64 模块的单元测试.


在一个网页中, 你可以进行Base64的加密和解密,通过使用函数btoa() and atob() .不幸的是这些函数依附在window对象: 由于这个对象在你的add-on(插件) main 的代码里不是有效对象,所以 atob() and btoa() 也不是有效的. 因此我们将展示如何在这个平台上创建一个base64模块 .

To begin with, create a new directory, navigate to it, and run cfx init. Now create a new file in "lib" called "base64.js", and give it the following contents:

const { atob, btoa } = require("chrome").Cu.import("resource://gre/modules/Services.jsm", {});
exports.atob = a => atob(a);
exports.btoa = b => btoa(b);

This code exports two functions, which just call the platform's btoa() and atob() functions. To show the module in use, edit the "main.js" file as follows:

var base64 = require("./base64");

var button = require("sdk/ui/button/action").ActionButton({
  id: "base64",
  label: "base64",
  icon: "./icon-16.png",
  onClick: function() {
    encoded = base64.btoa("hello");
    decoded = base64.atob(encoded);

To run this example you'll also have to have an icon file named "icon-16.png" saved in your add-ons "data" directory. You could download this icon: .

Now "main.js" imports the base64 module and calls its two exported functions. If we run the add-on and click the button, we should see the following logging output:

info: aGVsbG8=
info: hello

Testing the Base64 Module

Navigate to the add-on's test directory and delete the test-main.js file. In its place create a file called test-base64.js with the following contents:

var base64 = require("./base64");
exports["test atob"] = function(assert) {
      assert.ok(base64.atob("aGVsbG8=") == "hello", "atob works");
exports["test btoa"] = function(assert) {
  assert.ok(base64.btoa("hello") == "aGVsbG8=", "btoa works");
exports["test empty string"] = function(assert) {
  assert.throws(function() {
                "empty string check works");

This file: exports three functions, each of which expects to receive a single argument which is an assert object. assert is supplied by the test/assert module and implements the CommonJS Unit Testing specification.

  • The first two functions call atob() and btoa() and use assert.ok() to check that the output is as expected.

  • The second function tests the module's error-handling code by passing an empty string into atob() and using assert.throws() to check that the expected exception is raised.

At this point your add-on ought to look like this:


Now execute cfx --verbose test from the add-on's root directory. You should see something like this:

Running tests on Firefox 13.0/Gecko 13.0 ({ec8030f7-c20a-464f-9b0e-13a3a9e97384}) under darwin/x86.
info: executing 'test-base64.test atob'
info: pass: atob works
info: executing 'test-base64.test btoa'
info: pass: btoa works
info: executing 'test-base64.test empty string'
info: pass: empty string check works

3 of 3 tests passed.
Total time: 5.172589 seconds
Program terminated successfully.

What happens here is that cfx test:

Note the hyphen after "test" in the module name. cfx test will include a module called "test-myCode.js", but will exclude modules called "test_myCode.js" or "testMyCode.js".

  • looks in the test directory of your package
  • loads any modules whose names start with the word test-
  • calls each exported function whose name starts with "test", passing it an assert object as its only argument.

Obviously, you don't have to pass the --verbose option to cfx if you don't want to; doing so just makes the output easier to read.