// counter.service.ts
import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class CounterService {
  private count = 0;

  increment() { this.count++; }
  decrement() { this.count--; }
  reset() { this.count = 0; }
  getCount() { return this.count; }
}

// counter.service.spec.ts
import { TestBed } from '@angular/core/testing';
import { CounterService } from './counter.service';

describe('CounterService', () => {
  let service: CounterService;

  beforeEach(() => {
    TestBed.configureTestingModule({});
    service = TestBed.inject(CounterService);
  });

  it('starts at 0', () => {
    expect(service.getCount()).toBe(0);
  });

  it('increments the count', () => {
    service.increment();
    service.increment();
    expect(service.getCount()).toBe(2);
  });

  it('decrements the count', () => {
    service.increment();
    service.decrement();
    expect(service.getCount()).toBe(0);
  });

  it('resets the count', () => {
    service.increment();
    service.reset();
    expect(service.getCount()).toBe(0);
  });
});

/*
  Notes:
  - beforeEach gives each `it` a fresh CounterService via
    TestBed.inject, so tests don't bleed state into each other.
  - TestBed.inject pulls the service through the real DI system, the
    same way a component would receive it in the running app.
*/