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

Chạy ng generate component test -cd OnPush và kiểm tra các tệp component được tạo ra cùng tệp .spec, tập trung vào cách Angular component schematic thiết lập các bài kiểm thử. Sử dụng hướng dẫn kiểm thử Angular được liên kết làm ngữ cảnh, sau đó xác minh rằng bài kiểm thử được tạo sử dụng mẫu test host component và các lần gọi lặp lại fixture.detectChanges() sẽ gọi cơ chế phát hiện thay đổi.

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 😓)