Angular -如何在单元测试中模拟外部函数？

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

describe('Component', () => {
  let myService: MyService;

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [MyService]
    });

    myService = TestBed.inject(MyService);
  });

  it('should call external function with the correct arguments', () => {
    const externalFunctionSpy = spyOn(myService, 'externalFunction');
    const expectedArg = 'test argument';

    myService.callExternalFunction(expectedArg);

    expect(externalFunctionSpy).toHaveBeenCalledWith(expectedArg);
  });
});

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

describe('Component', () => {
  let myService: MyService;

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [MyService]
    });

    myService = TestBed.inject(MyService);
  });

  it('should call external function with the correct arguments', () => {
    const externalFunctionSpy = jasmine.createSpy('externalFunctionSpy');
    const expectedArg = 'test argument';

    myService.externalFunction = externalFunctionSpy;

    myService.callExternalFunction(expectedArg);

    expect(externalFunctionSpy).toHaveBeenCalledWith(expectedArg);
  });
});