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测试实用工具 API

Testing Utility APIs

本页面描述了一些最有用的 Angular 测试特性。

This page describes the most useful Angular testing features.

Angular 测试实用工具包括 TestBedComponentFixture 以及一些控制测试环境的函数。 TestBedComponentFixture 类是单独介绍的。

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.

下面是一些独立函数的摘要,以使用频率排序:

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

函数

Function

说明

Description

waitForAsync

在一个特殊的 async 测试区域中运行测试(it)的函数体或准备函数(beforeEach)。 参阅前面的讨论

Runs the body of a test (it) or setup (beforeEach) function within a special async test zone. See discussion above.

fakeAsync

在一个特殊的 fakeAsync 测试区域中运行测试(it)的函数体,以便启用线性风格的控制流。 参阅前面的讨论

Runs the body of a test (it) within a special fakeAsync test zone, enabling a linear control flow coding style. See discussion above.

tick

通过在 fakeAsync 测试区域中刷新定时器和微任务(micro-task)队列来仿真时间的流逝以及异步活动的完成。

Simulates the passage of time and the completion of pending asynchronous activities by flushing both timer and micro-task queues within the fakeAsync test zone.

好奇和执着的读者可能会喜欢这篇长博客: "Tasks, microtasks, queues and schedules".

The curious, dedicated reader might enjoy this lengthy blog post, "Tasks, microtasks, queues and schedules".

接受一个可选参数,它可以把虚拟时钟往前推进特定的微秒数。 清除调度到那个时间帧中的异步活动。 参阅前面的讨论

Accepts an optional argument that moves the virtual clock forward by the specified number of milliseconds, clearing asynchronous activities scheduled within that timeframe. See discussion above.

inject

从当前的 TestBed 注入器中把一个或多个服务注入到一个测试函数中。 它不能用于注入组件自身提供的服务。 参阅 debugElement.injector部分的讨论。

Injects one or more services from the current TestBed injector into a test function. It cannot inject a service provided by the component itself. See discussion of the debugElement.injector.

discardPeriodicTasks

fakeAsync 测试程序以正在运行的计时器事件任务(排队中的 setTimeOutsetInterval 的回调)结束时, 测试会失败,并显示一条明确的错误信息。

When a fakeAsync() test ends with pending timer event tasks (queued setTimeOut and setInterval callbacks), the test fails with a clear error message.

一般来讲,测试程序应该以无排队任务结束。 当待执行计时器任务存在时,调用 discardPeriodicTasks 来触发任务队列,防止该错误发生。

In general, a test should end with no queued tasks. When pending timer tasks are expected, call discardPeriodicTasks to flush the task queue and avoid the error.

flushMicrotasks

fakeAsync 测试程序以待执行微任务(比如未解析的承诺)结束时,测试会失败并显示明确的错误信息。

When a fakeAsync() test ends with pending micro-tasks such as unresolved promises, the test fails with a clear error message.

一般来说,测试应该等待微任务结束。 当待执行微任务存在时,调用 flushMicrotasks 来触发微任务队列,防止该错误发生。

In general, a test should wait for micro-tasks to finish. When pending microtasks are expected, call flushMicrotasks to flush the micro-task queue and avoid the error.

ComponentFixtureAutoDetect

一个服务提供者令牌,用于开启自动变更检测

A provider token for a service that turns on automatic change detection.

getTestBed

获取当前 TestBed 实例。 通常用不上,因为 TestBed 的静态类方法已经够用。 TestBed 实例有一些很少需要用到的方法,它们没有对应的静态方法。

Gets the current instance of the TestBed. Usually unnecessary because the static class methods of the TestBed class are typically sufficient. The TestBed instance exposes a few rarely used members that are not available as static methods.

TestBed 类摘要

TestBed class summary

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 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.

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

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

      
      type TestModuleMetadata = {
  providers?: any[];
  declarations?: any[];
  imports?: any[];
  schemas?: Array<SchemaMetadata | any[]>;
};
    

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。

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.

      
      type MetadataOverride<T> = {
  add?: Partial<T>;
  remove?: Partial<T>;
  set?: Partial<T>;
};
    

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

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

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。

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

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

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

这里列出了最重要的静态方法,以使用频率排序:

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

方法

Methods

说明

Description

configureTestingModule

测试垫片(karma-test-shim, browser-test-shim)创建了初始测试环境和默认测试模块。 默认测试模块是使用基本声明和一些 Angular 服务替代品,它们是所有测试程序都需要的。

The testing shims (karma-test-shim, browser-test-shim) establish the initial test environment and a default testing module. The default testing module is configured with basic declaratives and some Angular service substitutes that every tester needs.

调用 configureTestingModule 来为一套特定的测试定义测试模块配置,添加和删除导入、(组件、指令和管道的)声明和服务提供者。

Call configureTestingModule to refine the testing module configuration for a particular set of tests by adding and removing imports, declarations (of components, directives, and pipes), and providers.

compileComponents

在配置好测试模块之后,异步编译它。 如果测试模块中的任何一个组件具有 templateUrlstyleUrls,那么你必须调用这个方法,因为获取组件的模板或样式文件必须是异步的。 参阅前面的讨论

Compile the testing module asynchronously after you've finished configuring it. You must call this method if any of the testing module components have a templateUrl or styleUrls because fetching component template and style files is necessarily asynchronous. See above.

调用完 compileComponents 之后,TestBed 的配置就会在当前测试期间被冻结。

After calling compileComponents, the TestBed configuration is frozen for the duration of the current spec.

createComponent

基于当前 TestBed 的配置创建一个类型为 T 的组件实例。 一旦调用,TestBed 的配置就会在当前测试期间被冻结。

Create an instance of a component of type T based on the current TestBed configuration. After calling compileComponent, the TestBed configuration is frozen for the duration of the current spec.

overrideModule

替换指定的 NgModule 的元数据。回想一下,模块可以导入其它模块。 overrideModule 方法可以深入到当前测试模块深处,修改其中一个内部模块。

Replace metadata for the given NgModule. Recall that modules can import other modules. The overrideModule method can reach deeply into the current testing module to modify one of these inner modules.

overrideComponent

替换指定组件类的元数据,该组件类可能嵌套在一个很深的内部模块中。

Replace metadata for the given component class, which could be nested deeply within an inner module.

overrideDirective

替换指定指令类的元数据,该指令可能嵌套在一个很深的内部模块中。

Replace metadata for the given directive class, which could be nested deeply within an inner module.

overridePipe

替换指定管道类的元数据,该管道可能嵌套在一个很深的内部模块中。

Replace metadata for the given pipe class, which could be nested deeply within an inner module.

inject

从当前 TestBed 注入器获取一个服务。

Retrieve a service from the current TestBed injector.

inject 函数通常都能胜任这项工作,但是如果它没法提供该服务时就会抛出一个异常。

The inject function is often adequate for this purpose. But inject throws an error if it can't provide the service.

如果该服务是可选的呢?

What if the service is optional?

TestBed.inject() 方法可以接受可选的第二参数,当 Angular 找不到指定的服务提供者时,就会返回该对象(下面这个例子中是 null ):

The TestBed.inject() method takes an optional second parameter, the object to return if Angular can't find the provider (null in this example):

app/demo/demo.testbed.spec.ts
      
      expect(TestBed.inject(NotProvided, null)).toBeNull();
    

调用了 TestBed.inject 之后然后通过调用,TestBed 的配置就会在当前测试期间被冻结。

After calling TestBed.inject, the TestBed configuration is frozen for the duration of the current spec.

initTestEnvironment

为整套测试的运行初始化测试环境。

Initialize the testing environment for the entire test run.

测试垫片(karma-test-shim, browser-test-shim)会为你调用它,所以你很少需要自己调用它。

The testing shims (karma-test-shim, browser-test-shim) call it for you so there is rarely a reason for you to call it yourself.

这个方法只能被调用一次。如果确实需要在测试程序运行期间改变这个默认设置,那么先调用 resetTestEnvironment

You may call this method exactly once. If you must change this default in the middle of your test run, call resetTestEnvironment first.

指定 Angular 编译器工厂,PlatformRef,和默认 Angular 测试模块。 以 @angular/platform-<platform_name>/testing/<platform_name> 的形式提供非浏览器平台的替代品。

Specify the Angular compiler factory, a PlatformRef, and a default Angular testing module. Alternatives for non-browser platforms are available in the general form @angular/platform-<platform_name>/testing/<platform_name>.

resetTestEnvironment

重设初始测试环境,包括默认测试模块在内。

Reset the initial test environment, including the default testing module.

少数 TestBed 实例方法没有对应的静态方法。它们很少被使用。

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

ComponentFixture

The ComponentFixture

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

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

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。

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

ComponentFixture 的属性

ComponentFixture properties

下面是对测试最重要的属性,以使用频率排序:

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

属性

Properties

说明

Description

componentInstance

TestBed.createComponent 创建的组件类实例。

The instance of the component class created by TestBed.createComponent.

debugElement

与组件根元素关联的 DebugElement

The DebugElement associated with the root element of the component.

debugElement 提供了在测试和调试期间深入探查组件及其 DOM 元素的功能。 它对于测试者是一个极其重要的属性。它的大多数主要成员在后面都有讲解。

The debugElement provides insight into the component and its DOM element during test and debugging. It's a critical property for testers. The most interesting members are covered below.

nativeElement

组件的原生根 DOM 元素。

The native DOM element at the root of the component.

changeDetectorRef

组件的 ChangeDetectorRef

The ChangeDetectorRef for the component.

在测试一个拥有 ChangeDetectionStrategy.OnPush 的组件,或者在组件的变化测试在你的程序控制下时,ChangeDetectorRef 是最重要的。

The ChangeDetectorRef is most valuable when testing a component that has the ChangeDetectionStrategy.OnPush method or the component's change detection is under your programmatic control.

ComponentFixture 的方法

ComponentFixture methods

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。

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.

下面是对测试最有用的方法。

Here are the most useful methods for testers.

方法

Methods

说明

Description

detectChanges

为组件触发一轮变化检查。

Trigger a change detection cycle for the component.

调用它来初始化组件(它调用 ngOnInit)。或者在你的测试代码改变了组件的数据绑定属性值后调用它。 Angular 不能检测到你已经改变了 personComponent.name 属性,也不会更新 name 的绑定,直到你调用了 detectChanges

Call it to initialize the component (it calls ngOnInit) and after your test code, change the component's data bound property values. Angular can't see that you've changed personComponent.name and won't update the name binding until you call detectChanges.

之后,运行 checkNoChanges,来确认没有循环更新,除非它被这样调用:detectChanges(false)

Runs checkNoChanges afterwards to confirm that there are no circular updates unless called as detectChanges(false);

autoDetectChanges

如果你希望这个夹具自动检测变更,就把这个设置为 true

Set this to true when you want the fixture to detect changes automatically.

当自动检测打开时,测试 fixture 监听 zone 事件,并调用 detectChanges。 当你的测试代码直接修改了组件属性值时,你还是要调用 fixture.detectChanges 来触发数据绑定更新。

When autodetect is true, the test fixture calls detectChanges immediately after creating the component. Then it listens for pertinent zone events and calls detectChanges accordingly. When your test code modifies component property values directly, you probably still have to call fixture.detectChanges to trigger data binding updates.

默认值是 false,喜欢对测试行为进行精细控制的测试者一般保持它为 false

The default is false. Testers who prefer fine control over test behavior tend to keep it false.

checkNoChanges

运行一次变更检测来确认没有待处理的变化。如果有未处理的变化,它将抛出一个错误。

Do a change detection run to make sure there are no pending changes. Throws an exceptions if there are.

isStable

如果 fixture 当前是稳定的,则返回 true。 如果有异步任务没有完成,则返回 false

If the fixture is currently stable, returns true. If there are async tasks that have not completed, returns false.

whenStable

返回一个承诺,在 fixture 稳定时解析。

Returns a promise that resolves when the fixture is stable.

要想在完成了异步活动或异步变更检测之后再继续测试,可以对那个承诺对象进行挂钩。 参阅 前面

To resume testing after completion of asynchronous activity or asynchronous change detection, hook that promise. See above.

destroy

触发组件的销毁。

Trigger component destruction.

DebugElement

DebugElement 提供了对组件的 DOM 的访问。

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

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。

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

下面是 DebugElement 最有用的成员,以使用频率排序。

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

成员

Member

说明

Description

nativeElement

与浏览器中 DOM 元素对应(WebWorkers 时,值为 null)。

The corresponding DOM element in the browser (null for WebWorkers).

query

调用 query(predicate: Predicate<DebugElement>) 会在子树的任意深度中查找并返回能和谓词函数匹配的第一个 DebugElement

Calling query(predicate: Predicate<DebugElement>) returns the first DebugElement that matches the predicate at any depth in the subtree.

queryAll

调用 queryAll(predicate: Predicate<DebugElement>) 会在子树的任意深度中查找能和谓词函数匹配的所有 DebugElement

Calling queryAll(predicate: Predicate<DebugElement>) returns all DebugElements that matches the predicate at any depth in subtree.

injector

宿主依赖注入器。 比如,根元素的组件实例注入器。

The host dependency injector. For example, the root element's component instance injector.

componentInstance

元素自己的组件实例(如果有)。

The element's own component instance, if it has one.

context

为元素提供父级上下文的对象。 通常是控制该元素的祖级组件实例。

An object that provides parent context for this element. Often an ancestor component instance that governs this element.

当一个元素被 *ngFor 重复,它的上下文为 NgForRow,它的 $implicit 属性值是该行的实例值。 比如,*ngFor="let hero of heroes" 里的 hero

When an element is repeated within *ngFor, the context is an NgForRow whose $implicit property is the value of the row instance value. For example, the hero in *ngFor="let hero of heroes".

children

DebugElement 的直接子元素。可以通过继续深入 children 来遍历这棵树。

The immediate DebugElement children. Walk the tree by descending through children.

DebugElement 还有 childNodes,即 DebugNode 对象列表。 DebugElementDebugNode 对象衍生,而且通常节点(node)比元素多。测试者通常忽略赤裸节点。

DebugElement also has childNodes, a list of DebugNode objects. DebugElement derives from DebugNode objects and there are often more nodes than elements. Testers can usually ignore plain nodes.

parent

DebugElement 的父级。如果 DebugElement 是根元素,parent 为 null。

The DebugElement parent. Null if this is the root element.

name

元素的标签名字,如果它是一个元素的话。

The element tag name, if it is an element.

triggerEventHandler

如果在该元素的 listeners 集合中有相应的监听器,就根据名字触发这个事件。 第二个参数是该处理器函数所需的事件对象。参阅前面

Triggers the event by its name if there is a corresponding listener in the element's listeners collection. The second parameter is the event object expected by the handler. See above.

如果事件缺乏监听器,或者有其它问题,考虑调用 nativeElement.dispatchEvent(eventObject)

If the event lacks a listener or there's some other problem, consider calling nativeElement.dispatchEvent(eventObject).

listeners

元素的 @Output 属性以及/或者元素的事件属性所附带的回调函数。

The callbacks attached to the component's @Output properties and/or the element's event properties.

providerTokens

组件注入器的查询令牌。 包括组件自己的令牌和组件的 providers 元数据中列出来的令牌。

This component's injector lookup tokens. Includes the component itself plus the tokens that the component lists in its providers metadata.

source

source 是在源组件模板中查询这个元素的处所。

Where to find this element in the source component template.

references

与模板本地变量(比如 #foo)关联的词典对象,关键字与本地变量名字配对。

Dictionary of objects associated with template local variables (e.g. #foo), keyed by the local variable name.

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

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 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":

app/demo/demo.testbed.spec.ts
      
      // Filter for DebugElements with a #content reference
const contentRefs = el.queryAll( de => de.references.content);
    

Angular 的 By 类为常用条件方法提供了三个静态方法:

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

  • By.all - 返回所有元素

    By.all - return all elements.

  • By.css(selector) - 返回符合 CSS 选择器的元素。

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

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

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

app/hero/hero-list.component.spec.ts
      
      // Can find DebugElement either by css selector or by directive
const h2 = fixture.debugElement.query(By.css('h2'));
const directive = fixture.debugElement.query(By.directive(HighlightDirective));