javascript - '.toMatchObject' 和 'objectContaining' 有什么区别

Question

我写了下面的测试:

it('Can decrement the current step', function () {
    expect(reducer(TestState, { type: 'GOTO_PREVIOUS_STEP' })).toMatchObject({ currentStep: 4 });
});

it('Can decrement the current step v2', function () {
    expect(reducer(TestState, { type: 'GOTO_PREVIOUS_STEP' })).toEqual(expect.objectContaining({ currentStep: 4 }));
});

这两个好像都通过了测试，有什么区别吗？它们之间有性能影响吗？

Answer 1

通过查看文档和我自己的实验来证实这一点，不同之处在于处理嵌套在作为期望传递的 props 中的对象。

如果期望对象有一个属性，包含一个对象，该对象包含实际对象的等效属性中的一些但不是全部属性，则:

• .toMatchObject() 仍然会通过，as seen in the docs .

• expect.objectContaining() 将失败(除非您使用 expect.objectContaining() 在期望对象本身中声明该属性)

示例(在 Jest 中测试):

  // objectContaining, with nested object, containing full props/values
  // PASSES
  expect({ position: { x: 0, y: 0 } }).toEqual(expect.objectContaining({
    position: {
      x: expect.any(Number),
      y: expect.any(Number)
    }
  }));

  // objectContaining, with nested object, containing partial props/values
  // FAILS
  expect({ position: { x: 0, y: 0 } }).toEqual(expect.objectContaining({
    position: {
      x: expect.any(Number)
    }
  }));

  // objectContaining, with nested object, also declared with objectContaining, containing partial props/values
  // PASSES
  expect({ position: { x: 0, y: 0 } }).toEqual(expect.objectContaining({
    position: expect.objectContaining({
      x: expect.any(Number)
    })
  }));

  // toMatchObject, with nested object, containing full props/values
  // PASSES
  expect({ position: { x: 0, y: 0 } }).toMatchObject({
    position: {
      x: expect.any(Number),
      y: expect.any(Number)
    }
  });

  // toMatchObject, with nested object, containing partial props/values
  // PASSES
  expect({ position: { x: 0, y: 0 } }).toMatchObject({
    position: {
      x: expect.any(Number)
    }
  });