This guide offers tips and techniques for testing Angular applications. Though this page includes some general testing principles and techniques, the focus is on testing applications written with Angular.

本章提供了一些测试Angular应用的提示和技巧。虽然这里讲述了一些常规测试理念和技巧，但是其重点是测试用Angular编写的应用。

Contents

目录

• Live examples

  在线例子

• Introduction to Angular testing

  Angular测试简介

  • Tools and technologies

    工具与技术

  • Setup

    环境设置

  • Isolated unit tests vs. the Angular testing utilities

    独立的单元测试 vs. Angular测试工具集

• The first karma test

  第一个Karma测试

  • Run with karma

    运行Karma

  • Test debugging

    调试测试代码

  • Try the live example

    试用在线例子

• Test a component

  测试一个组件

  • TestBed

    TestBed（测试台）

  • createComponent

  • ComponentFixture, DebugElement, and query(By.css)

    ComponentFixture, DebugElement, 和 query(By.css)

  • The tests

    测试

  • detectChanges: Angular change detection within a test

    detectChanges: 在测试中控制Angular的变更检测

  • Try the live example

    试试在线例子

  • Automatic change detection

    自动变更检测

• Test a component with an external template

  测试带有外部模板的组件

  • The first asynchronous beforeEach

    第一处异步代码：beforeEach

  • compileComponents

  • The second synchronous beforeEach

    第二处同步代码：beforeEach

  • Waiting for compileComponents

    等待 compileComponents

  • Try the live example

    试试在线例子

• Test a component with a service dependency

  测试依赖服务的组件

  • Provide service test doubles

    测试替身

  • Get injected services

    获取注入的服务

  • TestBed.get

  • Always get the service from an injector

    总是从注入器中取得服务

  • Final setup and tests

    最终设置与测试

• Test a component with an async service

  测试带有异步服务的组件

  • Spying on the real service

    监听真实的服务

  • Synchronous tests

    同步测试

  • The async funciton in it

    it中的async函数

  • whenStable

  • The fakeAsync function

    fakeAsync 函数

  • The tick function

    tick函数

  • jasmine.done

• Test a component with inputs and outputs

  测试带有输入属性和输出属性的组件

  • Test DashboardHeroComponent stand-alone

    单独测试DashboardHeroComponent

  • triggerEventHandler

• Test a component inside a test host component

  在宿主组件中测试组件

• Test a routed component

  测试路由组件

  • The inject helper function

    inject助手函数

  • Test a routed component with parameters

    测试带参数的路由组件

  • Create an Observable test double

    创建Observable测试桩（Stub）

  • Testing with the Observable test double

    使用Observable测试桩进行测试

• Use a page object to simplify setup

  使用page对象来简化设置

• Set up with module imports

  设置导入了其它模块的模块

• Import the feature module

  导入特性模块

• Override a component's providers

  改写（Override）组件的提供商

  • The overrideComponent method

    overrideComponent方法

  • Provide a spy-stub (HeroDetailServiceSpy)

    提供一个 监听桩（HeroDetailServiceSpy）

  • The override tests

    改写测试

  • More overrides

    更多的改写

• Test a RouterOutlet component

  测试RouterOutlet组件

  • Stubbing unneeded components

    模拟不需要的组件

  • Stubbing the RouterLink

    模拟RouterLink

  • By.directive and injected directives

    By.directive与注入的指令

  • What good are these tests?

    为什么要这样写测试？

• "Shallow component tests" with NO_ERRORS_SCHEMA

  使用NO_ERRORS_SCHEMA进行 "浅组件测试"

• Test an attribute directive

  测试属性型指令

• Isolated unit tests

  独立的单元测试

  • Services

    服务

  • Services with dependencies

    带依赖的服务

  • Pipes

    管道

  • Write Angular tests too

    写Angular测试

  • Components

    组件

• Angular testing utility APIs

  Angular单元测试工具类 API

  • TestBed class summary

    TestBed总结

  • The ComponentFixture

    ComponentFixture总结

  • ComponentFixture properties

    ComponentFixture的属性

  • The ComponentFixture methods

    ComponentFixture方法

  • DebugElement

    DebugElement详情

• Test environment setup files

  测试环境设置所需的文件

  • npm packages

    npm包

• FAQ: Frequently asked questions

  常见问题（FAQ）

It’s a big agenda. Fortunately, you can learn a little bit at a time and put each lesson to use.

以上主题繁多。幸运的是，你可以慢慢地阅读并立刻应用每一个主题。

Live examples

在线例子

This guide presents tests of a sample application that is much like the Tour of Heroes tutorial. The sample application and all tests in this guide are available as live examples for inspection, experiment, and download:

这篇指南会展示一个范例应用的所有测试，这个范例应用和《英雄指南》教程非常像。 本章中的这个范例应用及其所有测试都有在线例子，以供查看、试验和下载。

• A spec to verify the test environment.

  用于验证测试环境的规约。

• The first component spec with inline template.

  第一个带内联模板的组件规约。

• A component spec with external template.

  带外部模板的组件规约。

• The QuickStart seed's AppComponent spec.

  快速起步种子工程的AppComponent规约。

• The sample application to be tested.

  所要测试的范例应用。

• All specs that test the sample application.

  本范例应用的所有规约。

• A grab bag of additional specs.

  其它规约汇总。

Introduction to Angular Testing

Angular测试入门

This page guides you through writing tests to explore and confirm the behavior of the application. Testing does the following:

本章教你如何编写测试程序来探索和确认应用的行为。测试的作用有：

1. Guards against changes that break existing code (“regressions”).

   测试守护由于代码变化而打破已有代码(“回归”)的情况。

2. Clarifies what the code does both when used as intended and when faced with deviant conditions.

   不管代码被正确使用还是错误使用，测试程序起到澄清代码的作用。

3. Reveals mistakes in design and implementation. Tests shine a harsh light on the code from many angles. When a part of the application seems hard to test, the root cause is often a design flaw, something to cure now rather than later when it becomes expensive to fix.

   测试程序暴露设计和实现可能出现的错误。测试程序从很多角度为代码亮出警报灯。当应用程序很难被测试时， 其根本原因一般都是设计缺陷，这种缺陷最好立刻被修正，不要等到它变得很难被修复的时候才行动。

This chapter assumes that you know something about testing. Don't worry if you don't. There are plenty of books and online resources to get up to speed.

本章假设你熟悉测试。但是如果你不熟悉也没有关系。有很多书本和在线资源可以帮助你。

Tools and technologies

工具与技术

You can write and run Angular tests with a variety of tools and technologies. This guide describes specific choices that are known to work well.

你可以用多种工具和技术来编写和运行Angular测试程序。本章介绍了一些大家已经知道能良好工作的选择。

Setup

环境设置

There are two fast paths to getting started with unit testing.

要开始单元测试，有两条捷径：

1. Start a new project following the instructions in Setup.

   遵循环境设置中给出的步骤开始一个新项目。

2. Start a new project with the Angular CLI.

   使用Angular CLI创建新的项目。

Both approaches install npm packages, files, and scripts pre-configured for applications built in their respective modalities. Their artifacts and procedures differ slightly but their essentials are the same and there are no differences in the test code.

以上两种方法都安装在各自的模式下为应用预先配置的npm包、文件和脚本。它们的文件和规程有一点不同，但是它们的核心部分是一样的，并且在测试代码方面没有任何区别。

In this guide, the application and its tests are based on the setup instructions. For a discussion of the unit testing setup files, see below.

本章中，该应用及其测试都是基于环境设置步骤的。 对单元测试的环境设置文件的讨论，参见后面。

Isolated unit tests vs. the Angular testing utilites

独立单元测试 vs. Angular测试工具集

Isolated unit tests examine an instance of a class all by itself without any dependence on Angular or any injected values. The tester creates a test instance of the class with new, supplying test doubles for the constructor parameters as needed, and then probes the test instance API surface.

独立单元测试用于测试那些完全不依赖Angular或不需要注入值的类实例。 测试程序是所有new创建该类的实例，为构造函数参数提供所需的测试替身，然后测试该实例的API接口。

You should write isolated unit tests for pipes and services.

我们应该为管道和服务书写独立单元测试。

You can test components in isolation as well. However, isolated unit tests don't reveal how components interact with Angular. In particular, they can't reveal how a component class interacts with its own template or with other components.

我们也同样可以对组件写独立单元测试。 不过，独立单元测试无法体现组件与Angular的交互。 具体来说，就是不能发现组件类如何与它的模板或其它组件交互。

Such tests require the Angular testing utilities. The Angular testing utilities include the TestBed class and several helper functions from @angular/core/testing. They are the main focus of this guide and you'll learn about them when you write your first component test. A comprehensive review of the Angular testing utilities appears later in this guide.

这时你需要Angular测试工具集。 Angular测试工具集包括TestBed类和一些来自@angular/core/testing的助手函数。 本章将会重点讲解它们，通过第一个组件测试来讲解。 本章稍后的部分将展示Angular测试工具集的全貌。

But first you should write a dummy test to verify that your test environment is set up properly and to lock in a few basic testing skills.

但首先，我们要先随便写一个测试来验证测试环境是否已经就绪了，并掌握一些基础的测试技术。

The first karma test

第一个karma测试

Start with a simple test to make sure that the setup works properly.

编写简单的测试程序，来确认以上的配置是否工作正常。

Create a new file called 1st.spec.ts in the application root folder, src/app/

在应用的根目录app/创建新文件，名叫1st.spec.ts。

Put spec files somewhere within the src/app/ folder. The karma.conf.js tells karma to look for spec files there, for reasons explained below.

将测试程序spec放到app/文件夹下的任何位置。 karma.conf.js告诉Karma在这个文件夹中寻找测试程序spec文件，原因在 这里 有所解释。

Add the following code to src/app/1st.spec.ts.

添加下面的代码到app/1st.spec.ts。

Run with karma

运行Karma

Compile and run it in karma from the command line using the following command:

使用下面的命令从命令行中编译并在Karma中运行上面的测试程序。

The command compiles the application and test code and starts karma. Both processes watch pertinent files, write messages to the console, and re-run when they detect changes.

该命令编译应用及其测试代码，并启动Karma。 两个进程都监视相关文件，往控制台输入信息和检测到变化时自动重新运行。

After a few moments, karma opens a browser and starts writing to the console.

等一小段时间后，Karma便打开浏览器并开始向控制台输出。

Hide (don't close!) the browser and focus on the console output, which should look something like this:

隐藏（不要关闭）浏览器，查看控制台的输出，应该是这样的：

Both the compiler and karma continue to run. The compiler output is preceded by [0]; the karma output by [1].

编译器和Karma都会持续运行。编译器的输入信息前面有[0]，Karma的输出前面有[1]。

Change the expectation from true to false.

将期望从true变换为false。

The compiler watcher detects the change and recompiles.

编译器监视器检测到这个变化并重新编译。

The karma watcher detects the change to the compilation output and re-runs the test.

Karma监视器检测到编译器输出的变化，并重新运行测试。

It fails of course.

正如所料，测试结果是失败。

Restore the expectation from false back to true. Both processes detect the change, re-run, and karma reports complete success.

将期望从false恢复为true。两个进程都检测到这个变化，自动重新运行，Karma报告测试成功。

Test debugging

调试测试程序

Debug specs in the browser in the same way thatyou debug an application.

在浏览器中，像调试应用一样调试测试程序spec。

1. Reveal the karma browser window (hidden earlier).

   显示Karma的浏览器窗口（之前被隐藏了）。

2. Click the DEBUG button; it opens a new browser tab and re-runs the tests.

   点击“DEBUG”按钮；它打开一页新浏览器标签并重新开始运行测试程序

3. Open the browser's “Developer Tools” (Ctrl-Shift-I on windows; Command-Option-I in OSX).

   打开浏览器的“Developer Tools”(Windows上的Ctrl-Shift-I或者OSX上的`Command-Option-I)。

4. Pick the "sources" section.

   选择“sources”页

5. Open the 1st.spec.ts test file (Control/Command-P, then start typing the name of the file).

   打开1st.spec.ts测试文件（Control/Command-P, 然后输入文件名字）。

6. Set a breakpoint in the test.

   在测试程序中设置断点。

7. Refresh the browser, and it stops at the breakpoint.

   刷新浏览器...然后它就会停在断点上。

Try the live example

试试这个在线例子

You can also try this test as a in plunker. All of the tests in this guide are available as live examples.

你还可以在plunker的中试运行这个测试。 本章的所有测试都有相应的在线例子。

Test a component

测试一个组件

An Angular component is the first thing most developers want to test. The BannerComponent in src/app/banner-inline.component.ts is the simplest component in this application and a good place to start. It presents the application title at the top of the screen within an <h1> tag.

大多数开发人员首先要测试的就是Angular组件。 src/app/banner-inline.component.ts中的BannerComponent是这个应用中最简单的组件，也是一个好的起点。 它所表示的是屏幕顶部<h1>标签中的应用标题。

This version of the BannerComponent has an inline template and an interpolation binding. The component is probably too simple to be worth testing in real life but it's perfect for a first encounter with the Angular testing utilities.

这个版本的BannerComponent有一个内联模板和一个插值表达式绑定。 这个组件可能太简单，以至于在真实的项目中都不值得测试，但它却是首次接触Angular测试工具集时的完美例子。

The corresponding src/app/banner-inline.component.spec.ts sits in the same folder as the component, for reasons explained in the FAQ answer to "Why put specs next to the things they test?".

组件对应的src/app/banner-inline.component.spec.ts文件与该组件位于同一个目录中，原因详见FAQ中的 为什么要把测试规约文件放在被测试对象旁边？

Start with ES6 import statements to get access to symbols referenced in the spec.

在测试文件中，我们先用ES6的import语句来引入测试所需的符号。

Here's the describe and the beforeEach that precedes the tests:

测试前面的describe和beforeEach如下：

TestBed

TestBed is the first and most important of the Angular testing utilities. It creates an Angular testing module—an @NgModule class—that you configure with the configureTestingModule method to produce the module environment for the class you want to test. In effect, you detach the tested component from its own application module and re-attach it to a dynamically-constructed Angular test module tailored specifically for this battery of tests.

TestBed（测试台）是Angular测试工具集中的首要概念。 它创建Angular测试模块（一个@NgModule类），我们可以通过调用它的configureTestingModule方法来为要测试的类生成模块环境。 其效果是，你可以把被测试的组件从原有的应用模块中剥离出来，把它附加到一个动态生成的Angular测试模块上，而该测试模块可以为这些测试进行特殊裁剪。

The configureTestingModule method takes an @NgModule-like metadata object. The metadata object can have most of the properties of a normal Angular module.

configureTestingModule方法接受一个类似@NgModule的元数据对象。这个元数据对象具有标准Angular模块的大多数属性。

This metadata object simply declares the component to test, BannerComponent. The metadata lack imports because (a) the default testing module configuration already has what BannerComponent needs and (b) BannerComponent doesn't interact with any other components.

这里的元数据对象只是声明了要测试的组件BannerComponent。 这个元数据中没有imports属性，这是因为：(a) 默认的测试模块配置中已经有了BannerComponent所需的一切，(b) BannerComponent不需要与任何其它组件交互。

Call configureTestingModule within a beforeEach so that TestBed can reset itself to a base state before each test runs.

在beforeEach中调用configureTestingModule，以便TestBed可以在运行每个测试之前都把自己重置回它的基础状态。

The base state includes a default testing module configuration consisting of the declarables (components, directives, and pipes) and providers (some of them mocked) that almost everyone needs.

基础状态中包含一个默认的测试模块配置，它包含每个测试都需要的那些声明（组件、指令和管道）以及服务提供商（有些是Mock版）。

This default configuration is merely a foundation for testing an app. Later you'll call TestBed.configureTestingModule with more metadata that define additional imports, declarations, providers, and schemas to fit your application tests. Optional override methods can fine-tune aspects of the configuration.

这个默认的配置只是测试的基础性工作。稍后我们会调用TestBed.configureTestingModule来传入更多元数据，这些元数据定义了额外的 imports、declarations、providers和试用于这些测试的概要（Schema）。 可选的override方法可以微调配置的各个方面。

createComponent

After configuring TestBed, you tell it to create an instance of the component-under-test. In this example, TestBed.createComponent creates an instance of BannerComponent and returns a component test fixture.

在配置好TestBed之后，我们可以告诉它创建一个待测组件的实例。 在这个例子中，TestBed.createComponent创建了一个BannerComponent的实例，并返回一个组件测试夹具。

The createComponent method closes the current TestBed instance to further configuration. You cannot call any more TestBed configuration methods, not configureTestingModule nor any of the override... methods. If you try, TestBed throws an error.

createComponent方法封闭了当前的TestBed实例，以免将来再配置它。 我们不能再调用任何TestBed的方法修改配置：不能调用configureTestingModule或任何override...方法。如果这么做，TestBed就会抛出错误。

ComponentFixture, DebugElement, and query(By.css)

ComponentFixture、DebugElement 和 query(By.css)

The createComponent method returns a ComponentFixture, a handle on the test environment surrounding the created component. The fixture provides access to the component instance itself and to the DebugElement, which is a handle on the component's DOM element.

createComponent方法返回ComponentFixture，用来控制和访问已创建的组件所在的测试环境。 这个fixture提供了对组件实例自身的访问，同时还提供了用来访问组件的DOM元素的DebugElement对象。

The title property value is interpolated into the DOM within <h1> tags. Use the fixture's DebugElement to query for the <h1> element by CSS selector.

title属性被插值到DOM的<h1>标签中。 用CSS选择器从fixture的DebugElement中query``<h1>元素。

The query method takes a predicate function and searches the fixture's entire DOM tree for the first element that satisfies the predicate. The result is a different DebugElement, one associated with the matching DOM element.

query方法接受predicate函数，并搜索fixture的整个DOM树，试图寻找第一个满足predicate函数的元素。

The By class is an Angular testing utility that produces useful predicates. Its By.css static method produces a standard CSS selector predicate that filters the same way as a jQuery selector.

By类是Angular测试工具之一，它生成有用的predicate。 它的By.css静态方法产生标准CSS选择器 predicate，与JQuery选择器相同的方式过滤。

Finally, the setup assigns the DOM element from the DebugElement nativeElement property to el. The tests assert that el contains the expected title text.

最后，这个配置把DebugElement中的nativeElementDOM元素赋值给el属性。 测试程序将判断el是否包含期待的标题文本。

The tests

测试程序

Jasmine runs the beforeEach function before each of these tests

再每个测试程序之前，Jasmin都一次运行beforeEach函数：

These tests ask the DebugElement for the native HTML element to satisfy their expectations.

这些测试程序向DebugElement获取原生HTML元素，来满足自己的期望。

detectChanges: Angular change detection within a test

detectChanges：在测试中的Angular变更检测

Each test tells Angular when to perform change detection by calling fixture.detectChanges(). The first test does so immediately, triggering data binding and propagation of the title property to the DOM element.

每个测试程序都通过调用fixture.detectChanges()来通知Angular执行变更检测。第一个测试程序立刻这么做，触发数据绑定和并将title属性发送到DOM元素中。

The second test changes the component's title property and only then calls fixture.detectChanges(); the new value appears in the DOM element.

第二个测试程序在更改组件的title属性之后才调用fixture.detectChanges()。新值出现在DOM元素中。

In production, change detection kicks in automatically when Angular creates a component or the user enters a keystroke or an asynchronous activity (e.g., AJAX) completes.

在产品阶段，当Angular创建组件、用户输入或者异步动作（比如AJAX）完成时，自动触发变更检测。

The TestBed.createComponent does not trigger change detection. The fixture does not automatically push the component's title property value into the data bound element, a fact demonstrated in the following test:

TestBed.createComponent不会触发变更检测。该工具不会自动将组件的title属性值推送到数据绑定的元素，下面的测试程序展示了这个事实：

This behavior (or lack of it) is intentional. It gives the tester an opportunity to inspect or change the state of the component before Angular initiates data binding or calls lifecycle hooks.

这种行为（或者缺乏的行为）是有意为之。在Angular初始化数据绑定或者调用生命周期钩子之前，它给测试者机会来查看或者改变组件的状态。

Try the live example

试试在线例子

Take a moment to explore this component spec as a and lock in these fundamentals of component unit testing.

花点时间来浏览一下该组件的规约，比如，深入理解组件单元测试的这些基本原理。

Automatic change detection

自动变更检测

The BannerComponent tests frequently call detectChanges. Some testers prefer that the Angular test environment run change detection automatically. That's possible by configuring the TestBed with the ComponentFixtureAutoDetect provider . First import it from the testing utility library :

BannerComponent的测试频繁调用detectChanges。 有些测试人员更希望Angular的测试环境自动进行变更检测。 这可以通过为TestBed配置上ComponentFixtureAutoDetect提供商来做到。首先从测试工具库中导入它：

Then add it to the providers array of the testing module configuration:

然后把它添加到测试模块配置的providers数组中：

Here are three tests that illustrate how automatic change detection works.

下列测试阐明了自动变更检测的工作原理。

The first test shows the benefit of automatic change detection.

第一个测试程序展示了自动检测的好处。

The second and third test reveal an important limitation. The Angular testing environment does not know that the test changed the component's title. The ComponentFixtureAutoDetect service responds to asynchronous activities such as promise resolution, timers, and DOM events. But a direct, synchronous update of the component property is invisible. The test must call fixture.detectChanges() manually to trigger another cycle of change detection.

第二和第三个测试程序显示了一个重要的局限性。 Angular测试环境不会知道测试程序改变了组件的title属性。 自动检测只对异步行为比如承诺的解析、计时器和DOM时间作出反应。 但是直接修改组件属性值的这种同步更新是不会触发自动检测的。 测试程序必须手动调用fixture.detectChange()，来触发新一轮的变更检测周期。

Test a component with an external template

测试带有外部模板的组件

The application's actual BannerComponent behaves the same as the version above but is implemented differently. It has external template and css files, specified in templateUrl and styleUrls properties.

在实际应用中，BannerComponent的行为和刚才的版本相同，但是实现方式不同。 它有一个外部模板和CSS文件，通过templateUrl和styleUrls属性来指定。

That's a problem for the tests. The TestBed.createComponent method is synchronous. But the Angular template compiler must read the external files from the file system before it can create a component instance. That's an asynchronous activity. The previous setup for testing the inline component won't work for a component with an external template.

这些测试有一个问题。 TestBed.createComponent方法是同步的。 但是Angular模板编译器必须在创建组件实例之前先从文件系统中读取这些值，而这是异步的。 以前测试内联模板时使用的设置方式不适用于外部模板。

The first asynchronous beforeEach

第一个异步的beforeEach

The test setup for BannerComponent must give the Angular template compiler time to read the files. The logic in the beforeEach of the previous spec is split into two beforeEach calls. The first beforeEach handles asynchronous compilation.

BannerComponent测试的设置方式必须给Angular模板编译器一些时间来读取文件。 以前放在beforeEach中的逻辑被拆分成了两个beforeEach调用。 第一个beforeEach处理异步编译工作。

Notice the async function called as the argument to beforeEach. The async function is one of the Angular testing utilities and has to be imported.

注意async函数被用作调用beforeEach的参数。 async函数是Angular测试工具集的一部分，这里必须引入它。

It takes a parameterless function and returns a function which becomes the true argument to the beforeEach.

它接收一个无参数的函数，并返回一个函数，这个函数会作为实参传给beforeEach。

The body of the async argument looks much like the body of a synchronous beforeEach. There is nothing obviously asynchronous about it. For example, it doesn't return a promise and there is no done function to call as there would be in standard Jasmine asynchronous tests. Internally, async arranges for the body of the beforeEach to run in a special async test zone that hides the mechanics of asynchronous execution.

async参数的内容看起来非常像同步版beforeEach的函数体。 它并不能很明显的看出来这是异步函数。 比如它不返回承诺（Promise），并且也没有标准Jasmine异步测试时常用的done函数作为参数。 内部实现上，async会把beforeEach的函数体放进一个特殊的异步测试区（async test zone），它隐藏了异步执行的内部机制。

All this is necessary in order to call the asynchronous TestBed.compileComponents method.

这就是为了调用异步的TestBed.compileComponents方法所要做的一切。

compileComponents

The TestBed.configureTestingModule method returns the TestBed class so you can chain calls to other TestBed static methods such as compileComponents.

TestBed.configureTestingModule方法返回TestBed类，以便你可以链式调用TestBed的其它静态方法，比如compileComponents。

The TestBed.compileComponents method asynchronously compiles all the components configured in the testing module. In this example, the BannerComponent is the only component to compile. When compileComponents completes, the external templates and css files have been "inlined" and TestBed.createComponent can create new instances of BannerComponent synchronously.

TestBed.compileComponents方法会异步编译这个测试模块中配置的所有组件。 在这个例子中，BannerComponent是唯一要编译的组件。 当compileComponents完成时，外部组件和css文件会被“内联”，而TestBed.createComponent会用同步的方式创建一个BannerComponent的新实例。

In this example, TestBed.compileComponents only compiles the BannerComponent. Tests later in the guide declare multiple components and a few specs import entire application modules that hold yet more components. Any of these components might have external templates and css files. TestBed.compileComponents compiles all of the declared components asynchronously at one time.

在这个例子中，TestBed.compileComponents只会编译BannerComponent。 本章稍后的测试中会声明多个组件，并且少量规约中会导入包含多个组件的应用模块。所有这些组件都可能含有外部模板和css文件。 TestBed.compileComponents会同时异步编译所有这些声明的组件。

Calling compileComponents closes the current TestBed instance is further configuration. You cannot call any more TestBed configuration methods, not configureTestingModule nor any of the override... methods. The TestBed throws an error if you try.

compileComponents方法封闭了当前的TestBed实例，以免将来再配置它。 我们不能再调用任何TestBed的方法修改配置：不能调用configureTestingModule或任何override...方法。如果这么做，TestBed就会抛出错误。

The second synchronous beforeEach

第二个同步beforeEach

A synchronous beforeEach containing the remaining setup steps follows the asynchronous beforeEach.

这个同步的beforeEach包含异步beforeEach之后的其余步骤。

These are the same steps as in the original beforeEach. They include creating an instance of the BannerComponent and querying for the elements to inspect.

这些步骤和原来的beforeEach中相同。 包括创建BannerComponent实例和查询要审查的元素。

You can count on the test runner to wait for the first asynchronous beforeEach to finish before calling the second.

测试运行器（runner）会先等待第一个异步beforeEach函数执行完再调用第二个。

Waiting for compileComponents

等待compileComponents

The compileComponents method returns a promise so you can perform additional tasks immediately after it finishes. For example, you could move the synchronous code in the second beforeEach into a compileComponents().then(...) callback and write only one beforeEach.

compileComponents方法返回一个承诺，来让我们可以在它完成之后立即执行额外的任务。 比如，我们可以把第二个beforeEach中的同步代码移到一个compileComponents().then(...)回调中，从而只需要写一个beforeEach。

Most developers find that hard to read. The two beforeEach calls are widely preferred.

大多数开发人员会觉得这样不易读，因此，更多采用的还是写两个beforeEach调用的方式。

Try the live example

试试在线例子

Take a moment to explore this component spec as a .

稍微花点时间，在中看看该组件的规约。

Test a component with a dependency

测试有依赖的组件

Components often have service dependencies.

组件经常依赖其他服务。

The WelcomeComponent displays a welcome message to the logged in user. It knows who the user is based on a property of the injected UserService:

WelcomeComponent为登陆的用户显示一条欢迎信息。它从注入的UserService的属性得知用户的身份：

The WelcomeComponent has decision logic that interacts with the service, logic that makes this component worth testing. Here's the testing module configuration for the spec file, src/app/welcome.component.spec.ts:

WelcomeComponent有与服务进行交互的决策逻辑，这样的逻辑让这个组件值得测试。下面是spec文件的测试模块配置，src/app/welcome.component.spec.ts：

This time, in addition to declaring the component-under-test, the configuration adds a UserService provider to the providers list. But not the real UserService.

这次，在测试配置里不但声明了被测试的组件，而且在providers数组中添加了UserService依赖。但不是真实的UserService。

Provide service test doubles

提供服务替身

A component-under-test doesn't have to be injected with real services. In fact, it is usually better if they are test doubles (stubs, fakes, spies, or mocks). The purpose of the spec is to test the component, not the service, and real services can be trouble.

被测试的组件不一定要注入真正的服务。实际上，服务的替身（stubs, fakes, spies或者mocks）通常会更加合适。 spec的主要目的是测试组件，而不是服务。真实的服务可能自身有问题。

Injecting the real UserService could be a nightmare. The real service might ask the user for login credentials and attempt to reach an authentication server. These behaviors can be hard to intercept. It is far easier and safer to create and register a test double in place of the real UserService.

注入真实的UserService有可能很麻烦。真实的服务可能询问用户登录凭据，也可能试图连接认证服务器。 可能很难处理这些行为。所以在真实的UserService的位置创建和注册UserService替身，会让测试更加容易和安全。

This particular test suite supplies a minimal UserService stub that satisfies the needs of the WelcomeComponent and its tests:

这个测试套件提供了最小化的UserServicestub类，用来满足WelcomeComponent和它的测试的需求：

Get injected services

获取注入的服务

The tests need access to the (stub) UserService injected into the WelcomeComponent.

测试程序需要访问被注入到WelcomeComponent中的UserService（stub类）。

Angular has a hierarchical injection system. There can be injectors at multiple levels, from the root injector created by the TestBed down through the component tree.

Angular的注入系统是层次化的。 可以有很多层注入器，从根TestBed创建的注入器下来贯穿整个组件树。

The safest way to get the injected service, the way that always works, is to get it from the injector of the component-under-test. The component injector is a property of the fixture's DebugElement.

最安全并总是有效的获取注入服务的方法，是从被测试的组件的注入器获取。 组件注入器是fixture的DebugElement的属性。

TestBed.get

You may also be able to get the service from the root injector via TestBed.get. This is easier to remember and less verbose. But it only works when Angular injects the component with the service instance in the test's root injector. Fortunately, in this test suite, the only provider of UserService is the root testing module, so it is safe to call TestBed.get as follows:

你可以通过TestBed.get方法来从根注入器中获取服务。 它更容易被记住，也更加简介。 但是只有在Angular使用测试的根注入器中的那个服务实例来注入到组件时，它才有效。 幸运的是，在这个测试套件中，唯一的UserService提供商就是根测试模块，所以像下面这样调用TestBed.get很安全：

Always get the service from an injector

总是从注入器获取服务

Do not reference the userServiceStub object that's provided to the testing module in the body of your test. It does not work! The userService instance injected into the component is a completely different object, a clone of the provided userServiceStub.

请不要引用测试代码里提供给测试模块的userServiceStub对象。这样不行！ 被注入组件的userService实例是完全不一样的对象，它提供的是userServiceStub的克隆。

Final setup and tests

最后的设置和测试程序

Here's the complete beforeEach using TestBed.get:

这里是使用TestBed.get的完整beforeEach：

And here are some tests:

下面是一些测试程序:

The first is a sanity test; it confirms that the stubbed UserService is called and working.

第一个测试程序是合法测试程序，它确认这个被模拟的UserService是否被调用和工作正常。

The remaining tests confirm the logic of the component when the service returns different values. The second test validates the effect of changing the user name. The third test checks that the component displays the proper message when there is no logged-in user.

接下来的测试程序确认当服务返回不同的值时组件的逻辑是否工作正常。 第二个测试程序验证变换用户名字的效果。 第三个测试程序检查如果用户没有登录，组件是否显示正确消息。

Test a component with an async service

测试有异步服务的组件

Many services return values asynchronously. Most data services make an HTTP request to a remote server and the response is necessarily asynchronous.

许多服务异步返回值。大部分数据服务向远程服务器发起HTTP请求，响应必然是异步的。

The "About" view in this sample displays Mark Twain quotes. The TwainComponent handles the display, delegating the server request to the TwainService.

本例的About视图显示马克吐温的名言。 TwainComponent组件处理视图，并委派TwainService向服务器发起请求。

Both are in the src/app/shared folder because the author intends to display Twain quotes on other pages someday. Here is the TwainComponent.

两者都在app/shared目录里，因为作者计划将来在其它页面也显示马克吐温的名言。 下面是TwainComponent：

The TwainService implementation is irrelevant for this particular test. It is sufficient to see within ngOnInit that twainService.getQuote returns a promise, which means it is asynchronous.

TwainService的实现细节现在并不重要。 ngOnInit的twainService.getQuote返回承诺，所以显然它是异步的。

In general, tests should not make calls to remote servers. They should emulate such calls. The setup in this src/app/shared/twain.component.spec.ts shows one way to do that:

一般来讲，测试程序不应该向远程服务器发请求。 它们应该仿真这样的请求。src/app/shared/twain.component.spec.ts里的配置是其中一种伪造方法：

Spying on the real service

刺探(Spy)真实服务

This setup is similar to the welcome.component.spec setup. But instead of creating a stubbed service object, it injects the real service (see the testing module providers) and replaces the critical getQuote method with a Jasmine spy.

本配置与welcome.component.spec配置类似。 但是与其伪造服务对象，它注入了真实的服务（参见测试模块的providers），并用Jasmine的spy替换关键的getQuote方法。

The spy is designed such that any call to getQuote receives an immediately resolved promise with a test quote. The spy bypasses the actual getQuote method and therefore does not contact the server.

这个Spy的设计是，所有调用getQuote的方法都会收到立刻解析的承诺，得到一条预设的名言。Spy拦截了实际getQuote方法，所有它不会联系服务。

Here are the tests with commentary to follow:

下面是接下来带有注解的测试程序：

Synchronous tests

同步测试程序

The first two tests are synchronous. Thanks to the spy, they verify that getQuote is called after the first change detection cycle during which Angular calls ngOnInit.

前两个测试程序是同步的。 在Spy的帮助下，它们验证了在Angular调用ngOnInit期间发生的第一次变更检测后，getQuote被调用了。

Neither test can prove that a value from the service is displayed. The quote itself has not arrived, despite the fact that the spy returns a resolved promise.

两者都不能证明被显示的值是服务提供的。 虽然spy返回了解析的承诺，名言本身还没有到来。

This test must wait at least one full turn of the JavaScript engine before the value becomes available. The test must become asynchronous.

这个测试程序必须等待JavaScript引擎一整个回合，返回值才会有效。该测试程序必须要变成异步的。

The async function in it

it里的async函数方法

Notice the async in the third test.

注意第三个测试程序的async方法。

The async function is one of the Angular testing utilities. It simplifies coding of asynchronous tests by arranging for the tester's code to run in a special async test zone as discussed earlier when it was called in a beforeEach.

async函数是Angular TestBed的一部分。通过将测试代码放到特殊的异步测试区域来运行，async函数简化了异步测试程序的代码。就像以前讨论过的，它会在beforeEach中被调用。

Although async does a great job of hiding asynchronous boilerplate, some functions called within a test (such as fixture.whenStable) continue to reveal their asynchronous behavior.

虽然async做了很多工作来尽量隐藏异步特性，但在测试程序（比如fixture.whenStable）里面调用函数时，有时还是会体现它们的异步行为。

whenStable

The test must wait for the getQuote promise to resolve in the next turn of the JavaScript engine.

测试程序必须等待getQuote在JavaScript引擎的下一回合中被解析。

This test has no direct access to the promise returned by the call to twainService.getQuote because it is buried inside TwainComponent.ngOnInit and therefore inaccessible to a test that probes only the component API surface.

本测试对twainService.getQuote返回的承诺没有直接的访问，因为它被埋没在TwainComponent.ngOnInit里， 所以对于只测试组件API表面的测试来说，它是无法被访问的。

Fortunately, the getQuote promise is accessible to the async test zone , which intercepts all promises issued within the async method call no matter where they occur.

幸运的是，异步测试区域可以访问getQuote承诺，因为它拦截所有调用异步方法所发出的承诺，不管它们在哪儿。

The ComponentFixture.whenStable method returns its own promise, which resolves when the getQuote promise finishes. In fact, the whenStable promise resolves when all pending asynchronous activities within this test complete — the definition of "stable."

ComponentFixture.whenStable方法返回它自己的承诺，它在getQuote承诺完成时被解析。实际上，“stable”的意思是当所有待处理异步行为完成时的状态，在“stable”后whenStable承诺被解析。

Then the test resumes and kicks off another round of change detection (fixture.detectChanges), which tells Angular to update the DOM with the quote. The getQuote helper method extracts the display element text and the expectation confirms that the text matches the test quote.

然后测试程序继续运行，并开始另一轮的变更检测（fixture.detectChanges）,通知Angular使用名言来更新DOM。 getQuote辅助方法提取出显示元素文本，然后expect语句确认这个文本与预备的名言相符。

The fakeAsync function

fakeAsync函数方法

The fourth test verifies the same component behavior in a different way.

第四个测试程序用不同的方法验证同样的组件行为。

Notice that fakeAsync replaces async as the it argument. The fakeAsync function is another of the Angular testing utilities.

注意，在it的参数中，async被faceAsync替换。 fakeAsync是另一种Angular测试工具。

Like async, it takes a parameterless function and returns a function that becomes the argument to the Jasmine it call.

和async一样，它也接受无参数函数并返回一个函数，变成Jasmine的it函数的参数。

The fakeAsync function enables a linear coding style by running the test body in a special fakeAsync test zone.

fakeAsync函数通过在特殊的fakeAsync测试区域运行测试程序，让测试代码更加简单直观。

The principle advantage of fakeAsync over async is that the test appears to be synchronous. There is no then(...) to disrupt the visible flow of control. The promise-returning fixture.whenStable is gone, replaced by tick().

对于async来说，fakeAsync最重要的好处是测试程序看起来像同步的。里面没有任何承诺。 没有then(...)链来打断控制流。

The tick function

tick函数

The tick function is one of the Angular testing utilities and a companion to fakeAsync. You can only call it within a fakeAsync body.

tick函数是Angular测试工具之一，是fakeAsync的同伴。 它只能在fakeAsync的主体中被调用。

Calling tick() simulates the passage of time until all pending asynchronous activities finish, including the resolution of the getQuote promise in this test case.

调用tick()模拟时间的推移，直到全部待处理的异步任务都已完成，在这个测试案例中，包含getQuote承诺的解析。

It returns nothing. There is no promise to wait for. Proceed with the same test code that appeared in the whenStable.then() callback.

它不返回任何结果。没有任何承诺需要等待。 直接执行与之前在whenStable.then()的回调函数里相同的代码。

Even this simple example is easier to read than the third test. To more fully appreciate the improvement, imagine a succession of asynchronous operations, chained in a long sequence of promise callbacks.

虽然这个例子非常简单，但是它已经比第三个测试程序更易阅读。 为了更充分的体会fakeAsync的好处，试想一下一连串的异步操作，被一长串的承诺回调链在一起。

jasmine.done

While the async and fakeAsync functions greatly simplify Angular asynchronous testing, you can still fall back to the traditional Jasmine asynchronous testing technique.

虽然async和fakeAsync函数大大的简化了异步测试，你仍然可以回退到传统的Jasmine异步测试技术上。

You can still pass it a function that takes a done callback. Now you are responsible for chaining promises, handling errors, and calling done at the appropriate moment.

你仍然可以将接受 done回调的函数传给it。 但是，你必须链接承诺、处理错误，并在适当的时候调用done。

Here is a done version of the previous two tests:

下面是上面两个测试程序的done版本：

Although there is no direct access to the getQuote promise inside TwainComponent, the spy has direct access, which makes it possible to wait for getQuote to finish.

虽然我们对TwainComponent里的getQuote承诺没有直接访问，但是Spy有，所以才可能等待getQuote完成。

Writing test functions with done, while more cumbersome than async and fakeAsync, is a viable and occasionally necessary technique. For example, you can't call async or fakeAsync when testing code that involves the intervalTimer, as is common when testing async Observable methods.

写带有done回调的测试函数，虽然比async和fakeAsync函数笨拙，但是在少数偶然情况下却是很有必要的技巧。比如，当测试涉及intervalTimer的代码时，你就没法调用async和fakeAsync函数，在测试异步Observable函数时也一样。

Test a component with inputs and outputs

测试带有导入inputs和导出outputs的组件

A component with inputs and outputs typically appears inside the view template of a host component. The host uses a property binding to set the input property and an event binding to listen to events raised by the output property.

带有导入和导出的组件通常出现在宿主组件的视图模板中。 宿主使用属性绑定来设置输入属性，使用事件绑定来监听输出属性触发的事件。

The testing goal is to verify that such bindings work as expected. The tests should set input values and listen for output events.

测试的目的是验证这样的绑定和期待的那样正常工作。 测试程序应该设置导入值并监听导出事件。

The DashboardHeroComponent is a tiny example of a component in this role. It displays an individual hero provided by the DashboardComponent. Clicking that hero tells the DashboardComponent that the user has selected the hero.

DashboardHeroComponent是非常小的这种类型的例子组件。 它显示由DashboardCompoent提供的英雄个体。 点击英雄告诉DashbaordComponent用户已经选择了这个英雄。

The DashboardHeroComponent is embedded in the DashboardComponent template like this:

DashboardHeroComponent是这样内嵌在DashboardCompoent的模板中的：

The DashboardHeroComponent appears in an *ngFor repeater, which sets each component's hero input property to the looping value and listens for the component's selected event.

DashboardHeroComponent在*ngFor循环中出现，设置每个组件的heroinput属性到迭代的值，并监听组件的selected事件。

Here's the component's definition:

下面是组件的定义：

While testing a component this simple has little intrinsic value, it's worth knowing how. You can use one of these approaches:

虽然测试这么简单的组件没有什么内在价值，但是它的测试程序是值得学习的。 有下列候选测试方案：

• Test it as used by DashboardComponent.

  把它当作被DashbaordComponent使用的组件来测试

• Test it as a stand-alone component.

  把它当作独立的组件来测试

• Test it as used by a substitute for DashboardComponent.

  把它当作被DashbaordComponent的替代组件使用的组件来测试

A quick look at the DashboardComponent constructor discourages the first approach:

简单看看DashbaordComponent的构造函数就否决了第一种方案：

The DashboardComponent depends on the Angular router and the HeroService. You'd probably have to replace them both with test doubles, which is a lot of work. The router seems particularly challenging.

DashbaordComponent依赖Angular路由器和HeroService服务。 你必须使用测试替身替换它们两个，似乎过于复杂了。 路由器尤其具有挑战性。

The immediate goal is to test the DashboardHeroComponent, not the DashboardComponent, so, try the second and third options.

当前的任务是测试DashboardHeroComponent组件，而非DashbaordComponent，所以无需做不必要的努力。 让我们尝试第二和第三种方案。

Test DashboardHeroComponent stand-alone

独立测试DashboardHeroComponent

Here's the spec file setup.

下面是spec文件的设置。

The async beforeEach was discussed above. Having compiled the components asynchronously with compileComponents, the rest of the setup proceeds synchronously in a second beforeEach, using the basic techniques described earlier.

异步beforeEach已经在上面讨论过。 在使用compileComponents异步编译完组件后，接下来的设置执行另一个同步的beforeEach，使用之前解释过的基本知识。

Note how the setup code assigns a test hero (expectedHero) to the component's hero property, emulating the way the DashboardComponent would set it via the property binding in its repeater.

注意代码是如何将模拟英雄（expectedHero）赋值给组件的hero属性的，模拟了DashbaordComponent在它的迭代器中通过属性绑定的赋值方式。

The first test follows:

紧接着第一个测试程序：

It verifies that the hero name is propagated to template with a binding. Because the template passes the hero name through the Angular UpperCasePipe, the test must match the element value with the uppercased name:

它验证了英雄名字通过绑定被传递到模板了。这里有个额外步骤。模板将英雄名字传给Angular的UpperCasePipe， 所以测试程序必须使用大写名字来匹配元素的值：

The second test verifies click behavior. Clicking the hero should raise a selected event that the host component (DashboardComponent presumably) can hear:

第二个测试程序验证点击行为。点击英雄应该出发selected事件，可供宿主组件(DashbaordComponent)监听：

The component exposes an EventEmitter property. The test subscribes to it just as the host component would do.

这个组件公开EventEmitter属性。测试程序像宿主组件那样来描述它。

The heroEl is a DebugElement that represents the hero <div>. The test calls triggerEventHandler with the "click" event name. The "click" event binding responds by calling DashboardHeroComponent.click().

heroEl是个DebugElement，它代表了英雄所在的<div>。 测试程序用“click”事件名字来调用triggerEventHandler。 调用DashboardHeroComponent.click()时，“click”事件绑定作出响应。

If the component behaves as expected, click() tells the component's selected property to emit the hero object, the test detects that value through its subscription to selected, and the test should pass.

如果组件像期待的那样工作，click()通知组件的selected属性就会发出hero对象，测试程序通过订阅selected事件而检测到这个值，所以测试应该成功。

triggerEventHandler

The Angular DebugElement.triggerEventHandler can raise any data-bound event by its event name. The second parameter is the event object passed to the handler.

Angular的DebugElement.triggerEventHandler可以用事件的名字触发任何数据绑定事件。 第二个参数是传递给事件处理器的事件对象。

In this example, the test triggers a "click" event with a null event object.

本例中，测试程序用null事件对象触发“click”事件。

The test assumes (correctly in this case) that the runtime event handler—the component's click() method—doesn't care about the event object.

测试程序假设（在这里应该这样)运行时间的事件处理器——组件的click()方法——不关心事件对象。

Other handlers are less forgiving. For example, the RouterLink directive expects an object with a button property that identifies which mouse button was pressed. This directive throws an error if the event object doesn't do this correctly.

其它处理器将会更加严格。 比如，RouterLink指令期待事件对象，并且该对象具有button属性，代表了已被按下的鼠标按钮。 如果该事件对象不具备上面的条件，指令便会抛出错误。

Clicking a button, an anchor, or an arbitrary HTML element is a common test task.

点击按钮、链接或者任意HTML元素是很常见的测试任务。

Make that easy by encapsulating the click-triggering process in a helper such as the click function below:

把click触发过程封装到辅助方法中可以简化这个任务，比如下面的click辅助方法：

The first parameter is the element-to-click. If you wish, you can pass a custom event object as the second parameter. The default is a (partial) left-button mouse event object accepted by many handlers including the RouterLink directive.

第一个参数是用来点击的元素。如果你愿意，可以将自定义的事件对象传递给第二个参数。 默认的是（局部的）鼠标左键事件对象， 它被许多事件处理器接受，包括RouterLink指令。

Here's the previous test, rewritten using this click helper.

下面是使用了click辅助函数重新编写的上一个测试程序：

Test a component inside a test host component

在测试宿主组件中测试组件

在测试宿主组件中测试组件

In the previous approach, the tests themselves played the role of the host DashboardComponent. But does the DashboardHeroComponent work correctly when properly data-bound to a host component?

在前面的方法中，测试本身扮演了宿主组件DashbaordComponent的角色。 一种挥之不去的疑虑仍然存在：当正常数据绑定到宿主组件时，DashboardHeroComponent还会正常工作吗？

Testing with the actual DashboardComponent host is doable but seems more trouble than its worth. It's easier to emulate the DashboardComponent host with a test host like this one:

使用实际的DashbaordComponent宿主来测试是可行的，但是这么做似乎不合算。 像下面这样使用测试宿主组件来模拟DashbaordComponent显得更加容易：

The test host binds to DashboardHeroComponent as the DashboardComponent would but without the distraction of the Router, the HeroService, or even the *ngFor repeater.

测试宿主组件和DashboardComponent一样绑定DashboardHeroComponent，但是不用理会Router、HeroService服务，甚至*ngFor循环。

The test host sets the component's hero input property with its test hero. It binds the component's selected event with its onSelected handler, which records the emitted hero in its selectedHero property. Later, the tests check that property to verify that the DashboardHeroComponent.selected event emitted the right hero.

测试宿主将组件的hero导入属性设置为它的模拟英雄。 它将组件的selected事件绑定到它的onSelected处理器，使用selectedHero属性来记录发送来的英雄。 然后测试检查这个属性来验证DashboardHeroComponent.selected事件确实发送了正确的英雄。

The setup for the test-host tests is similar to the setup for the stand-alone tests:

配置使用测试宿主的测试程序与配置孤立测试相似：

This testing module configuration shows two important differences:

这个测试模块配置展示了两个非常重要的区别：

1. It declares both the DashboardHeroComponent and the TestHostComponent.

   它同时声明了DashboardHeroComponent和TestHostComponent。

2. It creates the TestHostComponent instead of the DashboardHeroComponent.

   它创建了TestHostComponent，而非DashboardHeroComponent。

The createComponent returns a fixture that holds an instance of TestHostComponent instead of an instance of DashboardHeroComponent.

createComponent返回的fixture里有TestHostComponent实例，而非DashboardHeroComponent组件实例。

Creating the TestHostComponent has the side-effect of creating a DashboardHeroComponent because the latter appears within the template of the former. The query for the hero element (heroEl) still finds it in the test DOM, albeit at greater depth in the element tree than before.

当然，创建TestHostComponent有创建DashboardHeroComponent的副作用，因为后者出现在前者的模板中。 英雄元素（heroEl)的查询语句仍然可以在测试DOM中找到它，尽管元素树比以前更深。

The tests themselves are almost identical to the stand-alone version:

这些测试本身和它们的孤立版本几乎相同：

Only the selected event test differs. It confirms that the selected DashboardHeroComponent hero really does find its way up through the event binding to the host component.

只有selected事件的测试不一样。它确保被选择的DashboardHeroComponent英雄确实通过事件绑定被传递到宿主组件。

Test a routed component

测试带路由器的组件

Testing the actual DashboardComponent seemed daunting because it injects the Router.

测试实际的DashbaordComponent似乎令人生畏，因为它注入了Router。

It also injects the HeroService, but faking that is a familiar story. The Router has a complicated API and is entwined with other services and application preconditions.

它同时还注入了HeroService，但是我们已经知道如何伪造它。 Router的API非常复杂，并且它缠绕了其它服务和许多应用的先决条件。

Fortunately, the DashboardComponent isn't doing much with the Router

幸运的是，DashbaordComponent没有使用Router做很多事情。

This is often the case. As a rule you test the component, not the router, and care only if the component navigates with the right address under the given conditions. Stubbing the router with a test implementation is an easy option. This should do the trick:

通常都是这样的。原则上，你测试的是组件，不是路由器，应该只关心在指定的条件下，组件是否导航到正确的地址。 用模拟类来替换路由器是一种简单的方案。下面的代码应该可以：

Now set up the testing module with the test stubs for the Router and HeroService, and create a test instance of the DashboardComponent for subsequent testing.

现在我们来利用Router和HeroService的测试stub类来配置测试模块，并为接下来的测试创建DashboardComponent的测试实例。

The following test clicks the displayed hero and confirms (with the help of a spy) that Router.navigateByUrl is called with the expected url.

下面的测试程序点击显示的英雄，并利用spy来确认Router.navigateByUrl被调用了，而且传进的url是所期待的值。

The inject function

inject函数

Notice the inject function in the second it argument.

注意第二个it参数里面的inject函数。

The inject function is one of the Angular testing utilities. It injects services into the test function where you can alter, spy on, and manipulate them.

inject函数是Angular测试工具之一。 它注入服务到测试函数，以供修改、监视和操纵。

The inject function has two parameters:

inject函数有两个参数：

1. An array of Angular dependency injection tokens.

   一列数组，包含了Angular依赖注入令牌

2. A test function whose parameters correspond exactly to each item in the injection token array.

   一个测试函数，它的参数与注入令牌数组里的每个项目严格的一一对应。

This example injects the Router from the current TestBed injector. That's fine for this test because the Router is, and must be, provided by the application root injector.

这个例子通过当前的TestBed注入器来注入Router。 对这个测试程序来说，这是没问题的，因为Router是（也必须是）由应用的根注入器来提供。

If you need a service provided by the component's own injector, call fixture.debugElement.injector.get instead:

如果你需要组件自己的注入器提供的服务，调用fixture.debugElement.injector.get：

The inject function closes the current TestBed instance to further configuration. You cannot call any more TestBed configuration methods, not configureTestingModule nor any of the override... methods. The TestBed throws an error if you try.

inject函数关闭当前TestBed实例，使它无法再被配置。 你不能再调用任何TestBed配置方法、configureTestModule或者任何override...方法，否则TestBed将抛出错误。

Test a routed component with parameters

测试带有路由和路由参数的组件

Clicking a Dashboard hero triggers navigation to heroes/:id, where :id is a route parameter whose value is the id of the hero to edit. That URL matches a route to the HeroDetailComponent.

点击Dashboard英雄触发导航到heros/:id，其中:id是路由参数，它的值是进行编辑的英雄的id。 这个URL匹配到HeroDetailComponent的路由。

The router pushes the :id token value into the ActivatedRoute.params Observable property, Angular injects the ActivatedRoute into the HeroDetailComponent, and the component extracts the id so it can fetch the corresponding hero via the HeroDetailService. Here's the HeroDetailComponent constructor:

路由器将:id令牌的值推送到ActivatedRoute.params可观察属性里， Angular注入ActivatedRoute到HeroDetailComponent中， 然后组件提取id，这样它就可以通过HeroDetailService获取相应的英雄。 下面是HeroDetailComponent的构造函数：

HeroDetailComponent subscribes to ActivatedRoute.params changes in its ngOnInit method.

HeroDetailComponent在它的ngOnInit方法中监听ActivatedRoute.params的变化。

A test can explore how the HeroDetailComponent responds to different id parameter values by manipulating the ActivatedRoute injected into the component's constructor.

通过操纵被注入到组件构造函数的ActivatedRoute服务，测试程序可以探索HeroDetailComponent是如何对不同的id参数值作出响应的。

By now you know how to stub the Router and a data service. Stubbing the ActivatedRoute follows the same pattern except for a complication: the ActivatedRoute.params is an Observable.

现在，你已经知道如何模拟Router和数据服务。 模拟ActivatedRoute遵循类似的模式，但是有个额外枝节：ActivatedRoute.params是可观察对象。

Create an Observable test double

可观察对象的测试替身

The hero-detail.component.spec.ts relies on an ActivatedRouteStub to set ActivatedRoute.params values for each test. This is a cross-application, re-usable test helper class. Consider placing such helpers in a testing folder sibling to the app folder. This sample keeps ActivatedRouteStub in testing/router-stubs.ts:

hero-detail.component.spec.ts依赖ActivatedRouteStub来为每个测试程序设置ActivatedRoute.params值。 它是跨应用、可复用的测试辅助类。 我们建议将这样的辅助类放到app目录下的名为testing的目录。 本例把ActivatedRouteStub放到testing/router-stubs.ts：

Notable features of this stub are:

这个stub类有下列值得注意的特征：

• The stub implements only two of the ActivatedRoute capabilities: params and snapshot.params.

  这个stub类只实现ActivatedRoute的两个功能：params和snapshot.params。

• BehaviorSubject drives the stub's params Observable and returns the same value to every params subscriber until it's given a new value.

  BehaviorSubject驱使这个stub类的params可观察对象，并为每个params的订阅者返回同样的值，直到它接受到新值。

• The HeroDetailComponent chains its expressions to this stub params Observable which is now under the tester's control.

  HeroDetailComponent链接它的表达式到这个stub类的params可观察对象，该对象现在被测试者的控制之下。

• Setting the testParams property causes the subject to push the assigned value into params. That triggers the HeroDetailComponent params subscription, described above, in the same way that navigation does.

  设置testParams属性导致subject将指定的值推送进params。它触发上面描述过的HeroDetailComponent的params订阅，和导航的方式一样。

• Setting the testParams property also updates the stub's internal value for the snapshot property to return.

  设置testParams属性同时更新这个stub类内部值，用于snapshot属性的返回。

Testing with the Observable test double

测试可观察对象的替身

Here's a test demonstrating the component's behavior when the observed id refers to an existing hero:

下面的测试程序是演示组件在被观察的id指向现有英雄时的行为：

When the id cannot be found, the component should re-route to the HeroListComponent. The test suite setup provided the same RouterStub described above which spies on the router without actually navigating. This test supplies a "bad" id and expects the component to try to navigate.

当无法找到id时，组件应该重新导航到HeroListComponent。 该测试套件配置与上面描述的RouterStub一样，它在不实际导航的情况下刺探路由器。 该测试程序提供了“坏”的id，期望组件尝试导航。

While this app doesn't have a route to the HeroDetailComponent that omits the id parameter, it might add such a route someday. The component should do something reasonable when there is no id.

虽然本应用没有在缺少id参数的时候，继续导航到HeroDetailComponent的路由，但是，将来它可能会添加这样的路由。 当没有id时，该组件应该作出合理的反应。

In this implementation, the component should create and display a new hero. New heroes have id=0 and a blank name. This test confirms that the component behaves as expected:

在本例中，组件应该创建和显示新英雄。 新英雄的id为零，name为空。本测试程序确认组件是按照预期的这样做的：

Use a page object to simplify setup

使用page对象来简化配置

The HeroDetailComponent is a simple view with a title, two hero fields, and two buttons.

HeroDetailComponent是带有标题、两个英雄字段和两个按钮的简单视图。

But there's already plenty of template complexity.

但是它已经有很多模板复杂性。

To fully exercise the component, the test needs a lot of setup:

要彻底测试该组件，测试程序需要一系列设置：

• It must wait until a hero arrives before *ngIf allows any element in DOM.

  它必须在*ngIf允许元素进入DOM之前，等待hero的到来

• It needs references to the title <span> and the name <input> so it can inspect their values.

  它需要标题名字span和名字输入框元素的引用，用来检查它们的值

• It needs references to the two buttons so it can click them.

  它需要两个按钮的引用，以便点击它们

• It needs spies for some of the component and router methods.

  刺探（spy）组件和路由器的方法

Even a small form such as this one can produce a mess of tortured conditional setup and CSS element selection.

即使是像这样一个很小的表单，也能产生令人疯狂的错综复杂的条件设置和CSS元素选择。

Tame the madness with a Page class that simplifies access to component properties and encapsulates the logic that sets them. Here's the Page class for the hero-detail.component.spec.ts

通过简化组件属性的访问和封装设置属性的逻辑，Page类可以轻松解决这个令人抓狂的难题。 下面是为hero-detail.component.spec.ts准备的page类：

Now the important hooks for component manipulation and inspection are neatly organized and accessible from an instance of Page.

现在，用来操作和检查组件的重要钩子都被井然有序的组织起来了，可以通过page实例来使用它们。

A createComponent method creates a page objectand fills in the blanks once the hero arrives.

createComponent方法创建page，在hero到来时，自动填补空白。

The observable tests in the previous section demonstrate how createComponent and page keep the tests short and on message. There are no distractions: no waiting for promises to resolve and no searching the DOM for element values to compare.

上一节的可观察对象测试展示了createComponent和page如何让测试程序简短和即时。 没有任何干扰：无需等待承诺的解析，也没有搜索DOM元素值进行比较。

Here are a few more HeroDetailComponent tests to drive the point home.

这里是一些更多的HeroDetailComponent测试程序，进一步的展示了这一点。

Setup with module imports

模块导入imports的配置

Earlier component tests configured the testing module with a few declarations like this:

此前的组件测试程序使用了一些declarations来配置模块，就像这样：

The DashboardComponent is simple. It needs no help. But more complex components often depend on other components, directives, pipes, and providers and these must be added to the testing module too.

DashbaordComponent非常简单。它不需要帮助。 但是更加复杂的组件通常依赖其它组件、指令、管道和提供商， 所以这些必须也被添加到测试模块中。

Fortunately, the TestBed.configureTestingModule parameter parallels the metadata passed to the @NgModule decorator which means you can also specify providers and imports.

幸运的是，TestBed.configureTestingModule参数与传入@NgModule装饰器的元数据一样，也就是所你也可以指定providers和imports.

The HeroDetailComponent requires a lot of help despite its small size and simple construction. In addition to the support it receives from the default testing module CommonModule, it needs:

虽然HeroDetailComponent很小，结构也很简单，但是它需要很多帮助。 除了从默认测试模块CommonModule中获得的支持，它还需要：

• NgModel and friends in the FormsModule to enable two-way data binding.

  FormsModule里的NgModel和其它，来进行双向数据绑定

• The TitleCasePipe from the shared folder.

  shared目录里的TitleCasePipe

• Router services (which these tests are stubbing).

  一些路由器服务（测试程序将stub伪造它们）

• Hero data access services (also stubbed).

  英雄数据访问服务（同样被stub伪造了）

One approach is to configure the testing module from the individual pieces as in this example:

一种方法是在测试模块中一一配置，就像这样：

Because many app components need the FormsModule and the TitleCasePipe, the developer created a SharedModule to combine these and other frequently requested parts. The test configuration can use the SharedModule too as seen in this alternative setup:

因为许多应用组件需要FormsModule和TitleCasePipe，所以开发者创建了SharedModule来合并它们和一些频繁需要的部件。 测试配置也可以使用SharedModule，请看下面另一种配置：

It's a bit tighter and smaller, with fewer import statements (not shown).

它的导入声明少一些（未显示），稍微干净一些，小一些。

Import the feature module

导入特性模块

The HeroDetailComponent is part of the HeroModule Feature Module that aggregates more of the interdependent pieces including the SharedModule. Try a test configuration that imports the HeroModule like this one:

HeroDetailComponent是HeroModule特性模块的一部分，它组合了更多互相依赖的部件，包括SharedModule。 试试下面这个导入HeroModule的测试配置：

That's really crisp. Only the test doubles in the providers remain. Even the HeroDetailComponent declaration is gone.

这样特别清爽。只有providers里面的测试替身被保留。连HeroDetailComponent声明都消失了。

Override a component's providers

重载组件的提供商

The HeroDetailComponent provides its own HeroDetailService.

HeroDetailComponent提供自己的HeroDetailService服务。

It's not possible to stub the component's HeroDetailService in the providers of the TestBed.configureTestingModule. Those are providers for the testing module, not the component. They prepare the dependency injector at the fixture level.

在TestBed.configureTestingModule的providers中stub伪造组件的HeroDetailService是不可行的。 这些是测试模块的提供商，而非组件的。组件级别的供应商应该在fixture级别准备的依赖注入器。

Angular creates the component with its own injector, which is a child of the fixture injector. It registers the component's providers (the HeroDetailService in this case) with the child injector. A test cannot get to child injector services from the fixture injector. And TestBed.configureTestingModule can't configure them either.

Angular创建组件时，该组件有自己的注入器，它是fixture注入器的子级。 Angular使用这个子级注入器来注册组件的提供商（也就是HeroDetailService）。 测试程序无法从fixture的注入器获取这个子级注入器。 而且TestBed.configureTestingModule也无法配置它们。

Angular has been creating new instances of the real HeroDetailService all along!

Angular始终都在创建真实HeroDetailService的实例。

What if you aren't so lucky. What if faking the HeroService is hard? What if HeroDetailService makes its own server requests?

如果我们没有这么幸运怎么办？如果伪造HeroService很难怎么办？如果HeroDetailService自己发出服务器请求怎么办？

The TestBed.overrideComponent method can replace the component's providers with easy-to-manage test doubles as seen in the following setup variation:

TestBed.overrideComponent方法可以将组件的providers替换为容易管理的测试替身，参见下面的设置变化：

Notice that TestBed.configureTestingModule no longer provides a (fake) HeroService because it's not needed.

注意，TestBed.configureTestingModule不再提供（伪造）HeroService，因为已经没有必要了。

The overrideComponent method

overrideComponent方法

Focus on the overrideComponent method.

注意这个overrideComponent方法。

It takes two arguments: the component type to override (HeroDetailComponent) and an override metadata object. The overide metadata object is a generic defined as follows:

它接受两个参数：要重载的组件类型(HeroDetailComponent)和用于重载的元数据对象。 重载元数据对象是泛型类，就像这样：

A metadata override object can either add-and-remove elements in metadata properties or completely reset those properties. This example resets the component's providers metadata.

元数据重载对象可以添加和删除元数据属性的项目，也可以彻底重设这些属性。 这个例子重新设置了组件的providers元数据。

The type parameter, T, is the kind of metadata you'd pass to the @Component decorator:

这个类型参数，T，是你会传递给@Component装饰器的元数据的类型。

Provide a spy stub (HeroDetailServiceSpy)

提供一个刺探桩（Spy stub）（HeroDetailServiceSpy）

This example completely replaces the component's providers array with a new array containing a HeroDetailServiceSpy.

这个例子把组件的providers数组完全替换成了一个包含HeroDetailServiceSpy的新数组。

The HeroDetailServiceSpy is a stubbed version of the real HeroDetailService that fakes all necessary features of that service. It neither injects nor delegates to the lower level HeroService so there's no need to provide a test double for that.

HeroDetailServiceSpy是实际HeroDetailService服务的桩版本，它伪造了该服务的所有必要特性。 但它既不需要注入也不会委托给低层的HeroService服务，因此我们不用为HeroService提供测试替身。

The related HeroDetailComponent tests will assert that methods of the HeroDetailService were called by spying on the service methods. Accordingly, the stub implements its methods as spies:

通过对该服务的方法进行刺探，HeroDetailComponent的关联测试将会对HeroDetailService是否被调用过进行断言。 因此，这个桩类会把它的方法实现为刺探方法：

The override tests

重载的测试程序

Now the tests can control the component's hero directly by manipulating the spy-stub's testHero and confirm that service methods were called.

现在，测试程序可以通过操控stub的testHero，直接控制组件的英雄，并确保服务的方法被调用过。

More overrides

更多重载

The TestBed.overrideComponent method can be called multiple times for the same or different components. The TestBed offers similar overrideDirective, overrideModule, and overridePipe methods for digging into and replacing parts of these other classes.

TestBed.overrideComponent方法可以在相同或不同的组件中被反复调用。 TestBed还提供了类似的overrideDirective、overrideModule和overridePipe方法，用来深入并重载这些其它类的部件。

Explore the options and combinations on your own.

自己探索这些选项和组合。

Test a RouterOutlet component

测试带有RouterOutlet的组件

The AppComponent displays routed components in a <router-outlet>. It also displays a navigation bar with anchors and their RouterLink directives.

AppComponent在<router-outlet>中显示导航组件。 它还显示了导航条，包含了链接和它们的RouterLink指令。

The component class does nothing.

组件的类没有做任何事。

Unit tests can confirm that the anchors are wired properly without engaging the router. See why this is worth doing below.

在不涉及路由的情况下，单元测试可以确认链接的设置是否正确。 参见下面的内容，了解为什么值得这么做。

Stubbing unneeded components

stub伪造不需要的组件

The test setup should look familiar.

该测试配置应该看起来很眼熟：

The AppComponent is the declared test subject.

AppComponent是被声明的测试对象。

The setup extends the default testing module with one real component (BannerComponent) and several stubs.

使用一个真实的组件（BannerComponent）和几个stub，该配置扩展了默认测试模块。

• BannerComponent is simple and harmless to use as is.

  原样使用BannerComponent非常简单而且无害。

• The real WelcomeComponent has an injected service. WelcomeStubComponent is a placeholder with no service to worry about.

  真实的WelcomeComponent有被注入的服务。WelcomeStubComponent是无服务的替代品。

• The real RouterOutlet is complex and errors easily. The RouterOutletStubComponent (in testing/router-stubs.ts) is safely inert.

  真实的RouterOutlet很复杂而且容易出错。 testing/router-stubs.ts里的RouterOutletStubComponent是安全的替代品。

The component stubs are essential. Without them, the Angular compiler doesn't recognize the <app-welcome> and <router-outlet> tags and throws an error.

组件stub替代品很关键。 没有它们，Angular编译器无法识别<app-welcome和<router-outlet>标签，抛出错误。

Stubbing the RouterLink

Stub伪造RouterLink

The RouterLinkStubDirective contributes substantively to the test:

RouterLinkStubDirective为测试作出了重要的贡献：

The host metadata property wires the click event of the host element (the <a>) to the directive's onClick method. The URL bound to the [routerLink] attribute flows to the directive's linkParams property. Clicking the anchor should trigger the onClick method which sets the telltale navigatedTo property. Tests can inspect that property to confirm the expected click-to-navigation behavior.

host元数据属性将宿主元素(<a>)的click事件与指令的onClick方法关联起来。 绑定到[routerLink]的URL属性被传递到指令的linkParams属性。 点击这个链接应该能触发onClick方法，从而设置navigatedTo属性。 测试程序可以查看这个属性，来确认期望的点击导航行为。

By.directive and injected directives

By.directive和注入的指令

A little more setup triggers the initial data binding and gets references to the navigation links:

再一步配置触发了数据绑定的初始化，获取导航链接的引用：

Two points of special interest:

特别值得注意的两点：

1. You can locate elements by directive, using By.directive, not just by css selectors.

   你还可以按指令定位元素，使用By.directive，而不仅仅是通过CSS选择器。

2. You can use the component's dependency injector to get an attached directive because Angular always adds attached directives to the component's injector.

   你可以使用组件的依赖注入器来获取附加的指令，因为Angular总是将附加组件添加到组件的注入器中。

Here are some tests that leverage this setup:

下面是一些使用这个配置的测试程序：

What good are these tests?

这些测试有什么好处？

Stubbed RouterLink tests can confirm that a component with links and an outlet is setup properly, that the component has the links it should have, and that they are all pointing in the expected direction. These tests do not concern whether the app will succeed in navigating to the target component when the user clicks a link.

stub伪造的RouterLink测试可以确认带有链接和outlet的组件的设置的正确性，确认组件有应该有的链接，确认它们都指向了正确的方向。 这些测试程序不关心用户点击链接时，应用是否会成功的导航到目标组件。

Stubbing the RouterLink and RouterOutlet is the best option for such limited testing goals. Relying on the real router would make them brittle. They could fail for reasons unrelated to the component. For example, a navigation guard could prevent an unauthorized user from visiting the HeroListComponent. That's not the fault of the AppComponent and no change to that component could cure the failed test.

对于这样局限的测试目标，stub伪造RouterLink和RouterOutlet是最佳选择。 依靠真正的路由器会让它们很脆弱。 它们可能因为与组件无关的原因而失败。 例如，一个导航守卫可能防止没有授权的用户访问HeroListComponent。 这并不是AppComponent的过错，并且无论该组件怎么改变都无法修复这个失败的测试程序。

A different battery of tests can explore whether the application navigates as expected in the presence of conditions that influence guards such as whether the user is authenticated and authorized.

不同的测试程序可以探索在不同条件下（比如像检查用户是否认证），该应用是否和期望的那样导航。

"Shallow component tests" with NO_ERRORS_SCHEMA

使用NO_ERRORS_SCHEMA来“浅化”组件测试程序

The previous setup declared the BannerComponent and stubbed two other components for no reason other than to avoid a compiler error.

以前的配置声明了BannerComponent，并stub伪造了两个其它组件，仅仅是为了避免编译错误，不是为别的原因。

Without them, the Angular compiler doesn't recognize the <app-banner>, <app-welcome> and <router-outlet> tags in the app.component.html template and throws an error.

没有它们，Angular编译器无法识别app.component.html模板里的<app-banner>、<app-welcome>和<router-outlet>标签，并抛出错误。

Add NO_ERRORS_SCHEMA to the testing module's schemas metadata to tell the compiler to ignore unrecognized elements and attributes. You no longer have to declare irrelevant components and directives.

添加NO_ERRORS_SCHEMA到测试模块的schemas元数据中，告诉编译器忽略不认识的元素和属性。 这样你不再需要声明无关组件和指令。

These tests are shallow because they only "go deep" into the components you want to test. Here is a setup, with import statements, that demonstrates the improved simplicity of shallow tests, relative to the stubbing setup.

这些测试程序比较浅，因为它们只“深入”到你要测试的组件。 这里是一套配置（拥有import语句），体现了相比使用stub伪造的配置来说，浅测试程序的简单性。

The only declarations are the component-under-test (AppComponent) and the RouterLinkStubDirective that contributes actively to the tests. The tests in this example are unchanged.

这里唯一声明的是被测试的组件(AppComponent)和测试需要的RouterLinkStubDirective。 没有改变任何原测试程序。

Test an attribute directive

测试属性指令

An attribute directive modifies the behavior of an element, component or another directive. Its name reflects the way the directive is applied: as an attribute on a host element.

属性指令修改元素、组件和其它指令的行为。正如它们的名字所示，它们是作为宿主元素的属性来被使用的。

The sample application's HighlightDirective sets the background color of an element based on either a data bound color or a default color (lightgray). It also sets a custom property of the element (customProperty) to true for no reason other than to show that it can.

本例子应用的HighlightDirective使用数据绑定的颜色或者默认颜色来设置元素的背景色。 它同时设置元素的customProperty属性为true，这里仅仅是为了显示它能这么做而已，并无其它原因。

It's used throughout the application, perhaps most simply in the AboutComponent:

它的使用贯穿整个应用，也许最简单的使用在AboutComponent里：

Testing the specific use of the HighlightDirective within the AboutComponent requires only the techniques explored above (in particular the "Shallow test" approach).

使用AboutComponent来测试这个HightlightDirective的使用，只需要上面解释过的知识就够了，（尤其是"浅测试程序"方法)。

However, testing a single use case is unlikely to explore the full range of a directive's capabilities. Finding and testing all components that use the directive is tedious, brittle, and almost as unlikely to afford full coverage.

但是，测试单一的用例一般无法探索该指令的全部能力。 查找和测试所有使用该指令的组件非常繁琐和脆弱，并且通常无法覆盖所有组件。

Isolated unit tests might be helpful, but attribute directives like this one tend to manipulate the DOM. Isolated unit tests don't touch the DOMand, therefore , do not inspire confidence in the directive's efficacy.

孤立单元测试可能有用。 但是像这样的属性指令一般都操纵DOM。孤立单元测试不能控制DOM，所以不推荐用它测试指令的功能。

A better solution is to create an artificial test component that demonstrates all ways to apply the directive.

更好的方法是创建一个展示所有使用该组件的方法的人工测试组件。

Here are some tests of this component:

下面是一些该组件的测试程序：

A few techniques are noteworthy:

一些技巧值得注意：

• The By.directive predicate is a great way to get the elements that have this directive when their element types are unknown.

  当已知元素类型时，By.directive是一种获取拥有这个指令的元素的好方法。

• The :not pseudo-class in By.css('h2:not([highlight])') helps find <h2> elements that do not have the directive. By.css('*:not([highlight])') finds any element that does not have the directive.

  By.css('h2:not([highlight])')里的:not伪类（pseudo-class）帮助查找不带该指令的<h2>元素。By.css('*:not([highlight])')查找所有不带该指令的元素。

• DebugElement.styles affords access to element styles even in the absence of a real browser, thanks to the DebugElement abstraction. But feel free to exploit the nativeElement when that seems easier or more clear than the abstraction.

  DebugElement.styles让我们不借助真实的浏览器也可以访问元素的样式，感谢DebugElement提供的这层抽象！ 但是如果直接使用nativeElement会比这层抽象更简单、更清晰，也可以放心大胆的使用它。

• Angular adds a directive to the injector of the element to which it is applied. The test for the default color uses the injector of the second <h2> to get its HighlightDirective instance and its defaultColor.

  Angular将指令添加到它的元素的注入器中。默认颜色的测试程序使用第二个<h2>的注入器来获取它的HighlightDirective实例以及它的defaultColor。

• DebugElement.properties affords access to the artificial custom property that is set by the directive.

  DebugElement.properties让我们可以访问由指令设置的自定义属性。

Isolated Unit Tests

孤立的单元测试

Testing applications with the help of the Angular testing utilities is the main focus of this guide.

使用Angular测试工具测试应用程序是本章的重点。

However, it's often more productive to explore the inner logic of application classes with isolated unit tests that don't depend upon Angular. Such tests are often smaller and easier to read, write, and maintain.

但是，使用孤立单元测试来探索应用类的内在逻辑往往更加有效率，它不依赖Angular。 这种测试程序通常比较小、更易阅读、编写和维护。

They don't carry extra baggage:

它们不用背负额外的包袱：

• Import from the Angular test libraries.

  从Angular测试库导入

• Configure a module.

  配置模块

• Prepare dependency injection providers.

  准备依赖注入providers

• Call inject or async or fakeAsync.

  调用inject，或者async，或者fakeAsync

They follow patterns familiar to test developers everywhere:

它们会遵循测试时众所周知的模式：

• Exhibit standard, Angular-agnostic testing techniques.

  使用标准的、与Angular无关的测试技巧

• Create instances directly with new.

  直接使用new创建实例

• Substitute test doubles (stubs, spys, and mocks) for the real dependencies.

  用测试替身（stub，spy和mock）替代真正的依赖

Services

服务

Services are good candidates for isolated unit testing. Here are some synchronous and asynchronous unit tests of the FancyService written without assistance from Angular testing utilities.

服务是应用孤立测试的好例子。 下面是未使用Angular测试工具的一些FancyService的同步和异步单元测试：

A rough line count suggests that these isolated unit tests are about 25% smaller than equivalent Angular tests. That's telling but not decisive. The benefit comes from reduced setup and code complexity.

粗略行数表明，这些孤立单元测试比同等的Angular测试小25%。 这表明了它的好处，但是不是最关键的。 主要的好处来自于缩减的配置和代码的复杂性。

Compare these equivalent tests of FancyService.getTimeoutValue.

比较下面两个同等的FancyService.getTimeoutValue测试程序：

They have about the same line-count, but the Angular-dependent version has more moving parts including a couple of utility functions (async and inject). Both approaches work and it's not much of an issue if you're using the Angular testing utilities nearby for other reasons. On the other hand, why burden simple service tests with added complexity?

它们有类似的行数。 但是，依赖Angular的版本有更多活动的部分，包括一些工具函数（async和inject)。 两种方法都可行，而且如果你为了某些原因使用Angular测试工具，也并没有什么问题。 反过来，为什么要为简单的服务测试程序添加复杂度呢？

Pick the approach that suits you.

选择你喜欢的方法。

Services with dependencies

带依赖的服务

Services often depend on other services that Angular injects into the constructor. You can test these services without the TestBed. In many cases, it's easier to create and inject dependencies by hand.

服务通常依赖其它服务，Angular通过构造函数注入它们。 你可以不使用TestBed测试这些服务。 在许多情况下，创建和手动注入依赖来的更加容易。

The DependentService is a simple example:

DependentService是一个简单的例子：

It delegates its only method, getValue, to the injected FancyService.

它将唯一的方法，getValue，委托给了注入的FancyService。

Here are several ways to test it.

这里是几种测试它的方法。

The first test creates a FancyService with new and passes it to the DependentService constructor.

第一个测试程序使用new创建FancyService实例，并将它传递给DependentService构造函数。

However, it's rarely that simple. The injected service can be difficult to create or control. You can mock the dependency, use a dummy value, or stub the pertinent service method with a substitute method that 's easy to control.

很少有这么简单的，注入的服务有可能很难创建和控制。 你可以mock依赖，或者使用假值，或者用易于控制的替代品stub伪造相关服务。

These isolated unit testing techniques are great for exploring the inner logic of a service or its simple integration with a component class. Use the Angular testing utilities when writing tests that validate how a service interacts with components within the Angular runtime environment.

这些孤立单元测试技巧是一个很好的方法，用来探索服务的内在逻辑，以及它与组件类简单的集成。 当在运行时间环境下，使用Angular测试工具来验证一个服务是如何与组件互动的。

Pipes

管道

Pipes are easy to test without the Angular testing utilities.

管道很容易测试，无需Angular测试工具。

A pipe class has one method, transform, that manipulates the input value into a transformed output value. The transform implementation rarely interacts with the DOM. Most pipes have no dependence on Angular other than the @Pipe metadata and an interface.

管道类有一个方法，transform，用来转换输入值到输出值。 transform的实现很少与DOM交互。 除了@Pipe元数据和一个接口外，大部分管道不依赖Angular。

Consider a TitleCasePipe that capitalizes the first letter of each word. Here's a naive implementation with a regular expression.

假设TitleCasePipe将每个单词的第一个字母变成大写。 下面是使用正则表达式实现的简单代码：

Anything that uses a regular expression is worth testing thoroughly. Use simple Jasmine to explore the expected cases and the edge cases.

任何使用正则表达式的类都值得彻底的进行测试。 使用Jasmine来探索预期的用例和极端的用例。

Write Angular tests too

同时也编写Angular测试

These are tests of the pipe in isolation. They can't tell if the TitleCasePipe is working properly as applied in the application components.

有些管道的测试程序是孤立的。 它们不能验证TitleCasePipe是否在应用到组件上时是否工作正常。

Consider adding component tests such as this one:

考虑像这样添加组件测试程序：

Components

组件

Component tests typically examine how a component class interacts with its own template or with collaborating components. The Angular testing utilities are specifically designed to facilitate such tests.

组件测试通常检查该组件类是如何与自己的模板或者其它合作组件交互的。 Angular测试工具是专门为这种测试设计的。

Consider this ButtonComp component.

考虑这个ButtonComp组件。

The following Angular test demonstrates that clicking a button in the template leads to an update of the on-screen message.

下面的Angular测试演示点击模板里的按钮后，引起了屏幕上的消息的更新。

The assertions verify that the data values flow from one HTML control (the <button>) to the component and from the component back to a different HTML control (the <span>). A passing test means the component and its template are wired correctly.

该判断验证了数据绑定从一个HTML控件(<button>)流动到组件，以及从组件回到不同的HTML控件(<span>)。 通过的测试程序说明组件和它的模块是否设置正确。

Isolated unit tests can more rapidly probe a component at its API boundary, exploring many more conditions with less effort.

孤立单元测试可以更快的在API边界探测组件，更轻松的探索更多条件。

Here are a set of unit tests that verify the component's outputs in the face of a variety of component inputs.

下面是一套单元测试程序，用来验证面对多种输入时组件的输出。

Isolated component tests offer a lot of test coverage with less code and almost no setup. This is even more of an advantage with complex components, which may require meticulous preparation with the Angular testing utilities.

孤立组件单元测试使用更少的代码以及几乎不存在的配置，提供了很多测试覆盖率。 在测试复杂的组件时，这个优势显得更加明显，因为可能需要使用Angular测试工具进行精心准备。

On the other hand, isolated unit tests can't confirm that the ButtonComp is properly bound to its template or even data bound at all. Use Angular tests for that.

但是，孤立测试无法确认ButtonComp是否与其模板正确的绑定，或者是否有数据绑定。 使用Angular测试来应对它们。

Angular testing utility APIs

Angular测试工具API

This section takes inventory of the most useful Angular testing features and summarizes what they do.

本节将最有用的Angular测试功能提取出来，并总结了它们的作用。

The Angular testing utilities include the TestBed, the ComponentFixture, and a handful of functions that control the test environment. The TestBed and ComponentFixture classes are covered separately.

Angular测试工具包括TestBed、ComponentFixture和一些其他函数，用来控制测试环境。 TestBed和ComponentFixture在这里分别解释了。

Here's a summary of the stand-alone functions, in order of likely utility:

下面是一些独立函数的总结，以使用频率排序：

TestBed class summary

TestBed 类总结

The TestBed class is one of the principal Angular testing utilities. Its API is quite large and can be overwhelming until you've explored it, a little at a time. Read the early part of this guide first to get the basics before trying to absorb the full API.

TestBed类是Angular测试工具的主要类之一。它的API很庞大，可能有点过于复杂，直到你一点一点的探索它们。 阅读本章前面的部分，了解了基本的知识以后，再试着了解完整API。

The module definition passed to configureTestingModule is a subset of the @NgModule metadata properties.

传递给configureTestingModule的模块定义是@NgModule元数据属性的子集。

Each override method takes a MetadataOverride<T> where T is the kind of metadata appropriate to the method, that is, the parameter of an @NgModule, @Component, @Directive, or @Pipe.

每一个重载方法接受一个MetadataOverride<T>，这里T是适合这个方法的元数据类型，也就是@NgModule、@Component、@Directive或者@Pipe的参数。

The TestBed API consists of static class methods that either update or reference a global instance of theTestBed.

TestBed的API包含了一系列静态类方法，它们更新或者引用全局的TestBed实例。

Internally, all static methods cover methods of the current runtime TestBed instance , which is also returned by the getTestBed() function.

在内部，所有静态方法在getTestBed()函数返回的当前运行时间的TestBed实例上都有对应的方法。

Call TestBed methods within a beforeEach() to ensure a fresh start before each individual test.

在BeforeEach()内调用TestBed方法，这样确保在运行每个单独测试时，都有崭新的开始。

Here are the most important static methods, in order of likely utility.

这里列出了最重要的静态方法，以使用频率排序：

A few of the TestBed instance methods are not covered by static TestBed class methods. These are rarely needed.

少数TestBed实例方法没有对应的静态方法。它们很少被使用。

The ComponentFixture

ComponentFixture对象

The TestBed.createComponent<T> creates an instance of the component T and returns a strongly typed ComponentFixture for that component.

TestBed.createComponent<T>创建一个组件T的实例，并为该组件返回一个强类型的ComponentFixture。

The ComponentFixture properties and methods provide access to the component, its DOM representation, and aspects of its Angular environment.

ComponentFixture的属性和方法提供了对组件、它的DOM和它的Angular环境方面的访问。

ComponentFixture properties

ComponentFixture的属性

Here are the most important properties for testers, in order of likely utility.

下面是对测试最重要的属性，以使用频率排序：

ComponentFixture methods

ComponentFixture的方法

The fixture methods cause Angular to perform certain tasks on the component tree. Call these method to trigger Angular behavior in response to simulated user action.

fixture方法使Angular对组件树执行某些任务。 在触发Angular行为来模拟的用户行为时，调用这些方法。

Here are the most useful methods for testers.

下面是对测试最有用的方法。

DebugElement

The DebugElement provides crucial insights into the component's DOM representation.

DebugElement提供了对组件的DOM的访问。

From the test root component's DebugElement returned by fixture.debugElement, you can walk (and query) the fixture's entire element and component subtrees.

fixture.debugElement返回测试根组件的DebugElement，通过它你可以访问（查询）fixture的整个元素和组件子树。

Here are the most useful DebugElement members for testers, in approximate order of utility:

下面是DebugElement最有用的成员，以使用频率排序。

The DebugElement.query(predicate) and DebugElement.queryAll(predicate) methods take a predicate that filters the source element's subtree for matching DebugElement.

DebugElement.query(predicate)和DebugElement.queryAll(predicate)方法接受一个条件方法， 它过滤源元素的子树，返回匹配的DebugElement。

The predicate is any method that takes a DebugElement and returns a truthy value. The following example finds all DebugElements with a reference to a template local variable named "content":

这个条件方法是任何接受一个DebugElement并返回真值的方法。 下面的例子查询所有拥有名为content的模块本地变量的所有DebugElement：

The Angular By class has three static methods for common predicates:

Angular的By类为常用条件方法提供了三个静态方法：

• By.all - return all elements.

  By.all - 返回所有元素

• By.css(selector) - return elements with matching CSS selectors.

  By.css(selector) - 返回符合CSS选择器的元素。

• By.directive(directive) - return elements that Angular matched to an instance of the directive class.

  By.directive(directive) - 返回Angular能匹配一个指令类实例的所有元素。

Here's an example of Renderer tests from the live "Specs Bag" sample.

下面是在线“Specs Bag”例子中Renderer测试程序的例子

Test environment setup files

测试环境的设置文件

Unit testing requires some configuration and bootstrapping that is captured in setup files. The setup files for this guide are provided for you when you follow the Setup instructions. The CLI delivers similar files with the same purpose.

单元测试需要一些配置和启动代码，它们被收集到了这些设置文件中。 当你遵循环境设置中的步骤操作时，就会得到这些设置文件。 CLI工具也会生成类似的文件。

Here's a brief description of this guide's setup files:

下面是对本章中这些设置文件的简短说明：

npm packages

npm包

The sample tests are written to run in Jasmine and karma. The two "fast path" setups added the appropriate Jasmine and karma npm packages to the devDependencies section of the package.json. They're installed when you run npm install.

这些范例测试是为在Jasmine和karma而写的。 那两条“捷径”设置会把适当的Jasmine和Karma包添加到package.json的devDependencies区。 当我们运行npm install时，它们就会被安装上。

Why put specs next to the things they test?

为何将测试的spec配置文件放置到被测试文件的傍边？

It's a good idea to put unit test spec files in the same folder as the application source code files that they test:

我们推荐将单元测试的spec配置文件放到与应用程序源代码文件所在的同一个文件夹中，因为：

• Such tests are easy to find.

  这样的测试程序很容易被找到

• You see at a glance if a part of your application lacks tests.

  你可以一眼看出应用程序的那些部分缺乏测试程序。

• Nearby tests can reveal how a part works in context.

  临近的测试程序可以展示代码是如何在上下文中工作的

• When you move the source (inevitable), you remember to move the test.

  当你移动代码（无可避免）时，你记得一起移动测试程序

• When you rename the source file (inevitable), you remember to rename the test file.

  当你重命名源代码文件（无可避免），你记得重命名测试程序文件。

When would I put specs in a test folder?

什么时候我应该把测试spec文件放到测试目录中？

Application integration specs can test the interactions of multiple parts spread across folders and modules. They don't really belong to any part in particular, so they don't have a natural home next to any one file.

应用程序的整合测试spec文件可以测试横跨多个目录和模块的多个部分之间的互动。 它们不属于任何部分，很自然，没有特别的地方存放它们。

It's often better to create an appropriate folder for them in the tests directory.

通常，在test目录中为它们创建一个合适的目录比较好。

Of course specs that test the test helpers belong in the test folder, next to their corresponding helper files.

当然，测试助手对象的测试spec文件也属于test目录，与它们对应的助手文件相邻。