在執行一次昂貴的操作（例如HTTP GET）后，執行多個Mocha測試

Question

如果我要訪問一組URL：

let tests = [
  { status: 200, mediaType: 'text/html', req: { method: 'GET', uri: 'http://stackoverflow.com/' } },
  { status: 200, mediaType: 'text/html', req: { method: 'GET', uri: 'http://stackoverflow.com999/' } },
  { status: 200, mediaType: 'text/html', req: { method: 'GET999', uri: 'http://stackoverflow.com/' } },
]

以及要在每個測試上執行的一組測試：

it('should have status ' + test.status, () => {
  expect(test.response.statusCode).to.equal(test.status)
})
it('should have content type ' + test.mediaType, () => {
  let s = test.response.headers['content-type']
  let mediaType = s.indexOf(';') === -1 ? s : s.substr(0, s.indexOf(';'))
  expect(mediaType).to.equal(test.mediaType)
})
it('should have a body', () => {
  expect(test.body).to.not.equal('')
})

每組測試如何只執行一次昂貴的操作？ 另外，如果URL無法加載，我也不想運行測試。

Answer 1

Mocha Working With Promises文檔有一個示例，其中的每個測試（公認的）測試在執行前等待一個beforeEach承諾完成。 如果beforeEach需要一個beforeEach ，可以將那個諾言保存為beforeEach ，可以讓它們全部等待一個諾言：

let P = null
beforeEach(function () {
  if (!P) P = new Promise(...)
  return P
})

但更有可能的是，您只想使用before ：

beforeEach(function () {
  return new Promise(...)
})

有關問題的完整列表：

let expect = require('chai').expect
let request = require('request')

let tests = [
  { status: 200, mediaType: 'text/html', req: { method: 'GET', uri: 'http://localhost/' } },
  { status: 200, mediaType: 'text/html', req: { method: 'GET', uri: 'http://localhost999/' } },
  { status: 200, mediaType: 'text/html', req: { method: 'GET999', uri: 'http://localhost/' } },
]

tests.forEach(function (test) {
  describe(test.req.method + ' ' + test.req.uri, function () {
    before('should load', function() {
      return new Promise(function (resolve, reject) {
        request(test.req, function (error, response, body) {
          if (error) {
            reject(test.rejection = error)
          } else {
            test.response = response
            test.body = response
            resolve()
          }
        })
      })
    });

    it('should have status ' + test.status, () => {
      expect(test.response.statusCode).to.equal(test.status)
    })
    it('should have content type ' + test.mediaType, () => {
      let s = test.response.headers['content-type']
      let mediaType = s.indexOf(';') === -1 ? s : s.substr(0, s.indexOf(';'))
      expect(mediaType).to.equal(test.mediaType)
    })
    it('should have a body', () => {
      expect(test.body).to.not.equal('')
    })
  })
})

這使您的輸出相當流暢：

  GET http://stackoverflow.com/
    ✓ should have status 200
    ✓ should have content type text/html
    ✓ should have a body

  GET http://stackoverflow.com999/
    1) "before each" hook: should load for "should have status 200"

  GET999 http://stackoverflow.com/
    ✓ should have status 200
    ✓ should have content type text/html
    ✓ should have a body

如果將示例更改為使用stackoverflow的localhost intead，則可以查看訪問日志以確認每個URL均已加載一次：

127.0.0.1 - - [21/Oct/2017:06:52:10 -0400] "GET / HTTP/1.1" 200 12482 "-" "-"
127.0.0.1 - - [21/Oct/2017:06:52:10 -0400] "GET999 / HTTP/1.1" 501 485 "-" "-"

請注意，最后一個操作GET999 http://stackoverflow.com/給出了200的stackoverflow值（通過清漆緩存）和501的apache值：

  2) GET999 http://localhost/
       should have status 200:

      AssertionError: expected 501 to equal 200
      + expected - actual

      -501
      +200