在 Angular 中正确使用 TestBed

Question

在一个基于 Angular 8.1.2 和 Ionic 4 的应用程序项目中，我为 typescript 中的一个简单类编写了单元测试。这适用于“npm test”。为了准备需要模拟的更复杂的类，我将代码更改为使用 beforeEach 方法和 TestBed 对象：

import { CryptHelper, CryptCodeTyp, CryptIOStringTyp } from './cryptHelper';
import { TestBed } from '@angular/core/testing';

describe('CryptHelper', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [ CryptHelper ],
      imports: [ ],
      providers: [ CryptHelper ],
    }).compileComponents();
  });

  it('should be created', () => {
    let fixture = TestBed.createComponent(CryptHelper);
    let app = fixture.debugElement.componentInstance;
    expect(app).toBeDefined();
  });
});

这样我在测试输出中得到错误信息

error properties: Object({ ngSyntaxError: true })
Error: Unexpected value 'CryptHelper' declared by the module 'DynamicTestModule'. Please add a @Pipe/@Directive/@Component annotation.
    at syntaxError (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:2175:1)
    at http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:19889:1
    at <Jasmine>
    at CompileMetadataResolver.getNgModuleMetadata (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:19871:1)
    at JitCompiler._loadModules (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:25582:1)
    at JitCompiler._compileModuleAndAllComponents (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:25571:1)
    at JitCompiler.compileModuleAndAllComponentsAsync (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:25533:1)
    at CompilerImpl.compileModuleAndAllComponentsAsync (http://localhost:9876/_karma_webpack_/node_modules/@angular/platform-browser-dynamic/fesm2015/platform-browser-dynamic.js:237:1)
    at TestingCompilerImpl.compileModuleAndAllComponentsAsync (http://localhost:9876/_karma_webpack_/node_modules/@angular/platform-browser-dynamic/fesm2015/testing.js:140:1)
    at TestBedViewEngine.compileComponents (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/fesm2015/testing.js:3118:1)

我发现建议从声明中删除类名，

...
    TestBed.configureTestingModule({
      declarations: [ ],
...

但这导致我收到此错误消息：

error properties: Object({ ngSyntaxError: true })
Error: Illegal state: Could not load the summary for directive CryptHelper.
    at syntaxError (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:2175:1)
    at CompileMetadataResolver.getDirectiveSummary (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:19729:1)
    at JitCompiler.getComponentFactory (http://localhost:9876/_karma_webpack_/node_modules/@angular/compiler/fesm2015/compiler.js:25536:1)
    at CompilerImpl.getComponentFactory (http://localhost:9876/_karma_webpack_/node_modules/@angular/platform-browser-dynamic/fesm2015/platform-browser-dynamic.js:263:30)
    at TestingCompilerImpl.getComponentFactory (http://localhost:9876/_karma_webpack_/node_modules/@angular/platform-browser-dynamic/fesm2015/testing.js:148:1)
    at TestBedViewEngine.createComponent (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/fesm2015/testing.js:3418:1)
    at Function.createComponent (http://localhost:9876/_karma_webpack_/node_modules/@angular/core/fesm2015/testing.js:3000:1)
    at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/src/app/core/services/cryptHelper.spec.ts:15:27)
    at <Jasmine>

我找到了在声明中写类名的建议。但这导致我看到上面的错误消息。那我错了什么？欢迎任何帮助。

Answer 1

假设 CryptHelper 是一个组件：

    TestBed.configureTestingModule({
        declarations: [ CryptHelper], // Your testing component goes here
        providers: [ // Your component's providers goes here, for example a mocked service
            {
                provide: MyService, useValue: mockMyService
            }
        ],
        imports: [
            // imports from your component, for example MatDialogModule, MatInputModule, MyComponentModule, ...
        ]
    })
    .compileComponents();

假设 CryptHelper 是一个服务：

let cryptHelper: CryptHelper;

beforeEach(() => {
    TestBed.configureTestingModule({
        providers: [CryptHelper],
        imports: [] 
    });

    cryptHelper = TestBed.get(CryptHelper);
});

describe('CryptHelper Service creation', () => {
    it('should be created', inject([CryptHelper], (service: CryptHelper) => {
        expect(service).toBeTruthy();
    }));
});

Answer 2

正如您的日志所说，CryptHelper 不是一个组件。因此，正确的测试是将其用作服务（如果您希望像 DI 元素一样使用它）。 这是工作示例：

describe('CryptHelper', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [ CryptHelper ],
    });
  });

  it('should be created', () => {
    let fixture = TestBed.get(CryptHelper);
    let app = fixture.debugElement.componentInstance;
    expect(app).toBeDefined();
  });
});

你可以注意到TestBed.get 被用来代替TestBed.createComponent