如何对这个Angular打字机Http错误拦截器进行单元测试，该拦截器从一个管道的observable中捕获错误？

Question

我正在运行一个实验，我通过测试其他代码（例如自动化单元和端到端测试）来学习角度和打字稿。 在我接受测试之后，我计划将其重新用于我正在为大学教室工作的宠物项目。

我至少在这里通过单元测试代码的一半： http ： //jasonwatmore.com/post/2018/05/16/angular-6-user-registration-and-login-example-tutorial

我已经尝试了一段时间在单元测试下获得以下代码，但是我从我自己的想法或来自互联网的想法尝试的所有内容到目前为止都没有成功：

import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from "@angular/common/http";
import { AuthenticationService } from "src/app/authenticationService/AuthenticationService";
import { Observable, throwError } from "rxjs";
import { catchError } from "rxjs/operators";
import { Injectable } from "@angular/core";

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
    constructor(private authenticationService: AuthenticationService) {}

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        console.log('before error handle')
        return next.handle(request).pipe(catchError(err => {

            console.log('in error handle')

            if (err.status === 401) { 
                // auto logout if 401 response returned from api
                this.authenticationService.logout();
                location.reload(true);
            }

            const error = err.error.message || err.statusText;
            return throwError(error);
        }))
    }

}

以下测试代码和几个变体未能成功地在控制台日志中显示“错误处理”消息：

import { ErrorInterceptor } from "./ErrorInterceptor";
import { of, throwError, defer } from "rxjs";

describe('ErrorInterceptor', () => {
    let errorInterceptor;
    let authenticationServiceSpy;

    beforeEach(() => {
        authenticationServiceSpy = jasmine.createSpyObj('AuthenticationService', ['logout']);
        errorInterceptor = new ErrorInterceptor(authenticationServiceSpy);
    })

    it('should create', () => {
        expect(errorInterceptor).toBeTruthy();
    })

    describe('intercept', () => {
        let httpRequestSpy;
        let httpHandlerSpy;
        const error = {status: 401, statusText: 'error'};

        it('should auto logout if 401 response returned from api', () => {
            //arrange
            httpRequestSpy = jasmine.createSpyObj('HttpRequest', ['doesNotMatter']);
            httpHandlerSpy = jasmine.createSpyObj('HttpHandler', ['handle']);
            httpHandlerSpy.handle.and.returnValue({
                pipe: () => {
                return fakeAsyncResponseWithError({});
                }
            });

            //act
            errorInterceptor.intercept(httpRequestSpy, httpHandlerSpy);

            //assert
            //TBD

            function fakeAsyncResponseWithError<T>(data: T) {
                return defer(() => throwError(error));
            }
        })
    })
})

Answer 1

这里有几个问题。

• 首先，来自httpHandlerSpy.handle()返回值需要是一个Observable，因为它已经有了管道操作符，然后HttpInterceptor代码可以根据需要将它传递给catchError。
• 其次，HttpInterceptor返回一个Observable并为此“执行”，需要订阅它。

我把Stackblitz放在一起来演示我如何处理这个问题。

从Stackblitz，这是规范（ it功能）：

it('should auto logout if 401 response returned from api', () => {
    //arrange
    httpRequestSpy = jasmine.createSpyObj('HttpRequest', ['doesNotMatter']);
    httpHandlerSpy = jasmine.createSpyObj('HttpHandler', ['handle']);
    httpHandlerSpy.handle.and.returnValue(throwError(
        {error: 
            {message: 'test-error'}
        }
    ));
    //act
    errorInterceptor.intercept(httpRequestSpy, httpHandlerSpy)
        .subscribe(
            result => console.log('good', result), 
            err => { 
                console.log('error', err);
                expect(err).toEqual('test-error');
            }
        );

    //assert

})

我希望这有帮助。