javascript - Jest - 如何测试函数是否对参数进行了更改

Question

假设我有这个功能

function changeFooBarToOne(foo) {
  foo.bar = 1;
}

如何测试它是否将值更改为 1？

describe('changeFooBarToOne', () => {
  it('modifies the bar property value to 1', () => {
    const foo = { bar: 0 };
    // call the expect and evaluate foo to equal { bar: 1 }
  })
})

Answer 1

不要忘记，JavaScript 对象是引用类型。

function changeFooBarToOne(foo) {
   foo.bar = 1;
}

describe('changeFooBarToOne', () => {
  it('modifies the bar property value to 1', () => {
    const foo = { bar: 0 };
    changeFooBarToOne(foo);
    expect(foo.bar).toBe(1);
  })
})

//another way
describe('changeFooBarToOne_1', () => {
  it('modifies the bar property value to 1', () => {
    const foo = { bar: 0 };
    changeFooBarToOne(foo);
    expect(foo).toEqual({bar : 1});
  })
})