Issue: Unable to find solutions for all parameters in (?, ?)

Below is the unit test I've written for my Angular 10 component, which showcases a tree view with interactive features:

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { ReactiveFormsModule } from '@angular/forms';
// import { MatFormFieldModule } from '@angular/material/form-field';
// import { MatInputModule } from '@angular/material/input';
import { MatProgressBarModule } from '@angular/material/progress-bar';
import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
import { BrowserModule } from '@angular/platform-browser';
import { TreeviewModule } from 'ngx-treeview';
import { DocumentTreeService } from '../services/DocumentTreeService';

import { DocumentTreeviewComponent } from './document-treeview.component';

describe('DocumentTreeviewComponent', () => {
  let component: DocumentTreeviewComponent;
  let fixture: ComponentFixture<DocumentTreeviewComponent>;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ DocumentTreeviewComponent ],
      imports: [ TreeviewModule.forRoot(), ReactiveFormsModule, MatProgressBarModule,
         BrowserModule, MatProgressSpinnerModule, /* MatFormFieldModule, MatInputModule */ ],
      providers: [ DocumentTreeService ]
    })
    .compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(DocumentTreeviewComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

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

This is my DocumentTreeService.ts file:

import { HttpClient } from '@angular/common/http';
import { TreeviewItem } from 'ngx-treeview';
import { GlobalDataService } from './global-data.service';

interface TreeItem {
  name?: string;
  text: string;
  value: any;
  children?: String[];
  type: 'folder' | 'document';
}

/* tslint:disable no-string-literal prefer-for-of */
export class DocumentTreeService {

  constructor(public http: HttpClient, public DataService: GlobalDataService){}
  public treeviewmtextresponse;
  public docNames = [];

  public FolderItems = [];
  public treeviewItem = [];
  public finalTreeviewElements: TreeviewItem[] = [];

  getDocItems(): TreeviewItem[] {
    // implementation details
    }
}

I am encountering the following error message:

Error: Can't resolve all parameters for DocumentTreeService: (?, ?).

Even after verifying service placement and logic, the issue persists. What could be causing this problem?


Update 1

The codebase now includes:

 beforeEach(async () => {
    const httpSpy = jasmine.createSpyObj('HttpClient', ['get']);
    const dataSpy = jasmine.createSpyObj('GlobalDataService', ['funcName']);
    await TestBed.configureTestingModule({
      declarations: [ DocumentTreeviewComponent ],
      imports: [ TreeviewModule.forRoot(), ReactiveFormsModule, MatProgressBarModule,
         BrowserModule, MatProgressSpinnerModule, HttpClientTestingModule, MatDialogModule, MatInputModule
         /* MatFormFieldModule, MatInputModule */ ],
      providers: [ GlobalDataService, DatePipe,
        { provide: DocumentTreeService, useValue: mockDocumentTreeService },
        { provide: HttpClient, useValue: httpSpy },
        { provide: GlobalDataService, useValue: dataSpy }]
    })
    .compileComponents();

    documentTreeService = TestBed.inject(DocumentTreeService);
  });

Update 2

In document-treeview.component.ts:

import { Component, OnInit } from '@angular/core';
// remaining content remains unchanged

Answer №1

It is necessary for a service to include the @Injectable() decorator for the specified class.

For example:

@Injectable({providedIn: 'root'}) // Specify this if you want to provide it within a specific module scope. Remove the `providedIn` otherwise.
export class DocumentTreeService {...

If the issue persists, here is an alternative method for injecting services with dependencies.

let documentTreeService: DocumentTreeService;
beforeEach(async () => {
    For any function name that needs to exist on the spy objects,
    create a dataSpy using jasmine.createSpyObj('GlobalDataService', ['funcName']);
    await TestBed.configureTestingModule({
      //... code removed for simplicity
      imports: [HttpClientTestingModule, ...],
      providers: [
           DocumentTreeService,
      { provide: GlobalDataService, useValue: dataSpy }
      ]
    })
    .compileComponents();
   //To access the service in your tests
      documentTreeService = TestBed.inject(DocumentTreeService);
  });

Answer №2

Your DocumentTreeService is utilizing HttpClient and GlobalDataService without being provided in the TestBed module. To properly test the component, it's recommended to mock the DocumentTreeService instead of using the actual service.

describe('DocumentTreeviewComponent', () => {
  let component: DocumentTreeviewComponent;
  let fixture: ComponentFixture<DocumentTreeviewComponent>;
  let mockDocumentTreeService = jasmine.createSpyObj('documentTreeService', ['getDocItems']); // include this line for creating a mock  

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ DocumentTreeviewComponent ],
      imports: [ TreeviewModule.forRoot(), ReactiveFormsModule, MatProgressBarModule,
         BrowserModule, MatProgressSpinnerModule, /* MatFormFieldModule, MatInputModule */ ],
      providers: [{ provide: DocumentTreeService, useValue: mockDocumentTreeService }] // update this line to provide a mock
    })
    .compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(DocumentTreeviewComponent);
    component = fixture.componentInstance;
    mockDocumentTreeService.getDocItems().and.returnValue([]); // mocking getDocItems function to return an empty array
    fixture.detectChanges();
  });

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

Answer №3

When writing a unit test, it is important to only focus on testing the specific component and not its dependencies. One effective approach is to mock all other components that are declared, as well as any providers.

An excellent tool for this task is ng-mocks. With ng-mocks, you can easily mock your services without having to test them alongside your component.

providers: [ DocumentTreeService ]

This code snippet can be modified to:

providers: [ {
    provide: DocumentTreeService ,
    useValue: MockService(DocumentTreeService)
}]

By utilizing this method, you can effectively separate external services from your component's unit test.

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