Schematics for Component spec should use test host component when created with `-cd OnPush`

运行 ng generate component test -cd OnPush，检查生成的组件文件和 .spec 文件，重点关注 Angular component schematic 如何设置测试。以链接的 Angular 测试指南作为上下文，然后验证生成的测试使用了测试宿主组件模式，并且重复调用 fixture.detectChanges() 会触发变更检测。

Versions

Angular CLI: 1.7.3
Node: 8.9.1
OS: win32 x64
Angular: 5.2.1
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, platform-server, router

@angular/cli: 1.7.3
@angular-devkit/build-optimizer: 0.3.2
@angular-devkit/core: 0.3.2
@angular-devkit/schematics: 0.3.2
@ngtools/json-schema: 1.2.0
@ngtools/webpack: 1.10.2
@schematics/angular: 0.3.2
@schematics/package-update: 0.3.2
typescript: 2.4.2
webpack: 3.11.0

Repro steps

• ng generate component test -cd OnPush
• Edit the test.component.html to be

{{ checkMe() }}

• Add the checkMe method to test.component.ts:

checkMe() {
      console.log('change detection was invoked!');
}

• Edit the generated .spec file to include the following test:

fit('runs change detection', () => {
    fixture.detectChanges();
    fixture.detectChanges();
    fixture.detectChanges();
});

• Run unit test

Observed behavior

'change detection was invoked!' is logged only once (the initial check on creation of the component) rather than 4 times. That is to say, invoking fixture.detectChanges() does not actually run change detection. This is a known issue and is discussed in https://github.com/angular/angular/issues/12313

LOG: 'change detection was invoked!'
Chrome 65.0.3325 (Windows 10 0.0.0): Executed 1 of 478 SUCCESS (0 secs / 0.138 secs)

Desired behavior

As discussed in the thread linked above, the solution for testing OnPush components is to use the "test host component" pattern as described in the angular.io testing docs.

Therefore, the Angular CLI should use a schematic which uses the test host component when the -cd OnPush flag has been used. Otherwise we get a default test setup which is not fit for purpose (and will cause many wasted hours for devs like me 😓)