Step #1 to writing a great unit test file is scaffolding!

some-component.spec.ts

describe('SomeComponent:', () => {

  describe('someMethod', () => {

    describe('true', () => {

      it('should call depOne.doSomething', () => {

      });

      it('should return string \'eggs for breakfast\'', () => {

      });

    });

    describe('false', () => {

      it('should call depTwo.doSomethingElse', () => {

      });

      it('should return string \'steak for dinner\'', () => {

      });

    });

  });

  describe('returnSomeObservable', () => {

    it('should return a string Observable of \'test\'', () => {

    });

  });

  describe('subscribeAndDoSomething', () => {

    it('should call depThree.capitalize on the value \'jabroni\' emitted', () => {

    });

  });

});

some.component.ts

import { Observable } from 'rxjs';

import { DepOne, DepTwo, DepThree } from './dependencies';

export class SomeComponent {

  constructor(
    private depOne: DepOne,
    private depTwo: DepTwo,
    private depThree: DepThree
  ) { }

  someMethod(someCondition: boolean): string {
    if (someCondition) {
      this.depOne.doSomething();
      return 'eggs for breakfast';
    } else {
      this.depTwo.doSomethingElse();
      return 'steak for dinner';
    }
  }

  returnSomeObservable(): Observable<string> {
    return Observable.of('test');
  }

  subscribeAndDoSomething(): void {
    Observable.of('jabroni').subscribe((value) => {
      this.depThree.capitalize(value);
    });
  }

}