CODEWITHSUNDEEP
javascriptnode.jstypescriptjestjsnestjs
K S
K S

Reputation: 274

unit testing the interceptor with axios throws error

I'm writing Unit test for my Nestapp. For the interceptor file, I'm writing a test case to throw an error when error.message.indexOf('timeout') >= 0 and call Axios.Cancel with the error message.

But in my spec file I get : Cannot read property 'intercept' of undefined PFB my code and what am I missing here?

Can provide any mocks if required!

timeout.interceptor.ts

import {
    Injectable,
    NestInterceptor,
    CallHandler,
    HttpCode
} from '@nestjs/common';
import {
    Observable
} from 'rxjs';
import Axios from 'axios';


@Injectable()
export class TimeoutInterceptor implements NestInterceptor {
    intercept(context: any, next: CallHandler): Observable <any> {

        const CancelToken = Axios.CancelToken;
        const source = CancelToken.source();

        const url: string = context.url ? context.url : context.args[0].url;
        Axios.defaults.timeout = 200;


        Axios.get(url, {
            cancelToken: source.token
        }).then((res) => {}, error => {
            if (error.message.indexOf('timeout') >= 0) {
                throw new Axios.Cancel('Operation canceled due to timeout!');
            }
        }).catch((error) => {
            if (Axios.isCancel(error)) {
                console.log('Request canceled ', error);
            } else {
                console.log('--else part--');
            }
        });
        return next.handle();
    }
}
timeout.interceptor.spec.ts 
import {
    Test,
    TestingModule
} from '@nestjs/testing';
import {
    HttpModule,
    Controller,
    ExecutionContext,
    Get,
    InternalServerErrorException
} from '@nestjs/common';
import {
    of ,
    Observable,
    throwError
} from 'rxjs';
//import { Reflector } from '@nestjs/core';
import Axios from 'axios';

describe('Content Service', () => {
    let module: TestingModule;
    //let reflector;
    let timeoutInterceptor;
    //const loggerSpy = jest.fn()
    let getSpy;
    let cancelSpy;
    const errCode = 'MockController#decorated';
    const errMessage = 'Controller threw an error';


    beforeEach(async () => {
        module = await Test.createTestingModule({
            imports: [HttpModule],

        }).compile();

        getSpy = jest.spyOn(Axios, 'get');
        timeoutInterceptor = new timeoutInterceptor();
    })

    it('should call Axios.Cancel when it catches an timeout>0', done => {

        const context = {
            url: ''
        }
        timeoutInterceptor.intercept(context, throwError(new InternalServerErrorException()))
            .subscribe(
                () => {},
                () => {
                    expect(Axios.Cancel).toHaveBeenCalled();
                    done();
                }
            )
            .unsubscribe();
    });

});

Upvotes: 1

Views: 3472

Answers (1)

Kim Kern
Kim Kern

Reputation: 60557

You shouldn't use axios directly but nest's HttpService instead. Then it becomes much easier to test.

You can inject the HttpService via your interceptor's constructor:

export class TimeoutInterceptor implements NestInterceptor {
  constructor(httpService: HttpService) {}

This makes it much easier to test because you can use a mock for the HttpService (which is just a wrapper for axios) when you create an instance of your TimeoutInterceptor.

const httpMock = jest.fn(() => ({
  get: jest.fn(),
}))();
const interceptor = new TimeoutInterceptor(httpMock);

// mocked response
httpMock.get.mockReturnValue({...});
expect(interceptor.intercept(...)).toBe({...});
expect(httpMock.get).toHaveBeenCalled();

Upvotes: 1

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