Invalid provider for the NgModule 'DynamicTestModule' when testing a service in Angular 2

Question

I have the following service:

import { Injectable } from '@angular/core';

import { MenuItem } from './../classes/menu-item';
import { ITEMS } from './../static-data/items-list';

@Injectable()
export class ItemsListService {

    getItems(): Promise<MenuItem[]> {
        return Promise.resolve(ITEMS);
    }

}

The test for this service is here:

import { TestBed, async, inject } from '@angular/core/testing';

import { ItemListService } from './item-list.service';
import { MenuItem } from './../classes/menu-item';
import { ITEMS } from './../static-data/items-list';

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

  it('should ...', inject([ItemListService], (service: ItemListService) => {
    expect(service).toBeTruthy();
  }));
});

The MenuItem is defined here:

export class MenuItem {
    name: string;
    link: string;
}

ITEMS is defined here: import { MenuItem } from './../classes/menu-item';

export var ITEMS: MenuItem[] = [
    {name: 'Vehicles', link: '/vehicles'},
    {name: 'Gateways', link: '/gateways'},
    {name: 'Statuses', link: '/statuses'},
    {name: 'Logs', link: '/logs'}
]

When I run the test I am getting in the browsers console the followings errors:

FAILED ItemListService should ...

and

So why do I have these errors? And what is the solution for the test to work?

Solution 1

This is such an annoying error, thought I'd include another subtle cause to look for in your spec. In my case I specified providers instead of the correct value of provide as below

 TestBed.configureTestingModule({
      providers: [{provider: ApplicationActions, useClass: ActionMock}]

rather than offer useful information like "no 'provide' key specified" it simply reports

Failed: Invalid provider for the NgModule 'DynamicTestModule' - only instances of Provider and Type are allowed, got: [?[object Object]?, ...]

Solution 2

BTW also mind to use the class in providers, not some variable. This happened to me due to an accidental problematic replacement/casing:

Correct

 TestBed.configureTestingModule({
    // ...
    providers: [ SomeService ]
}

instead of...

Incorrect

 TestBed.configureTestingModule({
    // ...
    providers: [ someService ]
}

Note the camelCase variable (someService) is likely there if you use it in your test, that's why it does not throw a syntax error.

Solution 3

In my case, I had a stray comma in one of my provider lines, causing the DynamicTestModule to think I had passed an undefined definition.

        {
          provide: ApiService,
          useValue: {
            getUsers: jasmine
              .createSpy('getUsers')
              .and.returnValue(of({ status: 200, body: [] })),
          },
        },
        , // whoops!
        MessageService,
        { provide: Location, useValue: { back: jasmine.createSpy('back') } },

Comments

[AhmedRiyad]

Do you have any dependency in ItemListService ?

[Cristian]

No I don't have, but I found the issue. Check out the answer I have made.

[Fallenreaper]

and Check spelling and capitalization explicitly. When I was looking into this issue, it was because I used a capital letter instead of lowercase. Provide as opposed to provide

[nilsandrey]

Nice catch, just for being explicit I add the correct syntax: providers: [{provide: ApplicationActions, useClass: ActionMock}] or providers: [{provide: ApplicationActions, useValue: actionMockInstance}]

[dataphile]

It's provide not provider

[Kirk Sefchik]

This response is not useful.

[usalin]

I had this error because of an extra comma.