使用Sinon/Chai验证函数首次调用参数的问题求助

单元测试中匹配函数调用参数时遇到失败，测试代码如下：

beforeEach(() => {
  enrollmentOffer = offerReadModel(EnrollmentOfferStatuses.Accepted, false, undefined, true)
  fakeSearcher = buildFakeReadModelSearcher()
  ...
})
afterEach(() => {
  sinon.restore()
})

it('does the right query to get the latest child offer', async () => {
  await expect(calculateRenewInfo(enrollmentOffer as EnrollmentOfferReadModel, true)).to.be.fulfilled
  expect(fakeSearcher.filter).to.have.been.calledWithExactly({
    offerType: { eq: OfferTypes.Child },
    enrollmentOfferId: { eq: enrollmentOffer.id },
  })
})

测试报错信息：

22) calculateRenewInfo
     does the right query to get the latest child offer:
   AssertionError: expected filter to have been called with exact arguments {
offerType: { eq: 'child' },
enrollmentOfferId: { eq: '0a1a6e82-c2ca-48ec-9548-c4b5e4d26653' }
}
{ enrollmentOfferId: { eq: '0a1a6e82-c2ca-48ec-9548-c4b5e4d26653' } } {
offerType: { eq: 'child' },
enrollmentOfferId: { eq: '0a1a6e82-c2ca-48ec-9548-c4b5e4d26653' }
} 

问题核心：filter函数被调用了两次，第一次参数符合预期，第二次参数仅包含enrollmentOfferId，导致全局匹配失败。尝试使用firstCall属性时，TypeScript报错提示该属性不存在，因为类型系统无法识别fakeSearcher.filter是Sinon创建的fake函数。

fakeSearcher的构建代码：

export function buildFakeReadModelSearcher<TReadModel = unknown>(): Partial<Searcher<TReadModel>> {
  const fakeSearcher: Partial<Searcher<TReadModel>> = {}
  fakeSearcher.filter = sinon.fake.returns(fakeSearcher)
  fakeSearcher.afterCursor = sinon.fake.returns(fakeSearcher)
  fakeSearcher.paginatedVersion = sinon.fake.returns(fakeSearcher)
  fakeSearcher.limit = sinon.fake.returns(fakeSearcher)
  fakeSearcher.sortBy = sinon.fake.returns(fakeSearcher)
  fakeSearcher.search = sinon.fake.resolves({ items: [] })
  fakeSearcher.searchOne = sinon.fake.resolves(undefined)
  return fakeSearcher
}

需求：在尽量不修改buildFakeReadModelSearcher的前提下，仅验证filter首次调用的参数。

方法1：类型断言访问firstCall #

通过类型断言将fakeSearcher.filter转换为sinon.SinonFake类型，即可使用firstCall属性验证首次调用：

it('does the right query to get the latest child offer', async () => {
  await expect(calculateRenewInfo(enrollmentOffer as EnrollmentOfferReadModel, true)).to.be.fulfilled
  // 断言为SinonFake类型，解锁fake函数专属属性
  const filterFake = fakeSearcher.filter as sinon.SinonFake
  expect(filterFake.firstCall).to.have.been.calledWithExactly({
    offerType: { eq: OfferTypes.Child },
    enrollmentOfferId: { eq: enrollmentOffer.id },
  })
})

方法2：直接读取调用历史数组 #

Sinon的fake函数会将所有调用记录存储在callHistory数组中，通过类型断言后可直接取第一个元素的参数进行验证：

it('does the right query to get the latest child offer', async () => {
  await expect(calculateRenewInfo(enrollmentOffer as EnrollmentOfferReadModel, true)).to.be.fulfilled
  const filterFake = fakeSearcher.filter as sinon.SinonFake
  // 验证首次调用的第一个参数
  expect(filterFake.callHistory[0].args[0]).to.deep.equal({
    offerType: { eq: OfferTypes.Child },
    enrollmentOfferId: { eq: enrollmentOffer.id },
  })
})

方法3：结合调用次数限制验证 #

如果只需确保首次调用符合预期，可同时验证调用次数和参数，确保目标参数是第一次调用的传参：

it('does the right query to get the latest child offer', async () => {
  await expect(calculateRenewInfo(enrollmentOffer as EnrollmentOfferReadModel, true)).to.be.fulfilled
  const filterFake = fakeSearcher.filter as sinon.SinonFake
  // 验证目标参数被调用过一次（即首次调用）
  expect(filterFake).to.have.been.calledWithExactly({
    offerType: { eq: OfferTypes.Child },
    enrollmentOfferId: { eq: enrollmentOffer.id },
  }).once
})

内容的提问来源于stack exchange，提问作者Igor Shmukler