Angular 5 service failing to pass unit tests with (NullInjectorError: No provider for HttpClient!)

Question

The reason for "NullInjectorError: No provider for HttpClient!" are unresolved dependencies. In this case the lack of a HttpClientModule.

In your .service.spec.ts file add

  imports: [
        HttpClientTestingModule,
    ],

You might notice that I wrote HttpClientTestingModule instead of HttpClientModule. The reason is that we don't want to send actual http requests, but rather use a Mock API of the test framework.

simply add it like this,

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

Try wrapping your inject in an async, like below:

import { TestBed, async, inject } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { ApiService } from './api.service';

describe('ApiService', () => {
    beforeEach(() => {
      ...
    });    

  it(`should create`, async(inject([HttpTestingController, ApiService],
    (httpClient: HttpTestingController, apiService: ApiService) => {
      expect(apiService).toBeTruthy();
  })));

});

Don't forget to import async from @angular/core/testing.

I have had good success with this. It's the only different from your unit tests and mine where I use HttpClientTestingModule.

I have imports HttpClientModule and HttpClientTestingModule modules which resoved my issues.

import { HttpClientTestingModule } from '@angular/common/http/testing';
import {HttpClientModule} from '@angular/common/http';

  imports: [
        HttpClientModule,
        HttpClientTestingModule
      ]