.
├── bin
│   └── karma               # 命令运行入口
├── client                  # 浏览器内运行
│   ├── constants.js        # 变量模板，运行时由Node替换
│   ├── karma.js            # 主类:运行单元测试
│   ├── main.js             # 浏览器端入口文件
│   └── updater.js          # 更新运行状态到页面banner等
├── context                 # 用于iframe和parentWindow的沟通
│   ├── karma.js
│   └── main.js
├── lib                     # 服务端主要代码
│   ├── browser.js          # 控制浏览器状态 接收socket信息，发送EventEmit触发相应的事件
│   ├── browser_collection.js # 浏览器集合
│   ├── browser_result.js
│   ├── cli.js              # 入口文件
│   ├── completion.js
│   ├── config.js
│   ├── constants.js
│   ├── detached.js         # 分离运行karma
│   ├── emitter_wrapper.js
│   ├── events.js           # KarmaEventEmitter 事件
│   ├── executor.js         # 通知浏览器执行测试
│   ├── file-list.js        # 文件管理系统
│   ├── file.js
│   ├── helper.js
│   ├── index.js
│   ├── init
│   │   ├── color_schemes.js
│   │   ├── formatters.js
│   │   ├── log-queue.js
│   │   └── state_machine.js
│   ├── init.js             # karma init命令
│   ├── launcher.js         # 启动浏览器
│   ├── launchers
│   │   ├── base.js
│   │   ├── capture_timeout.js
│   │   ├── process.js
│   │   └── retry.js
│   ├── logger.js           # log4js 日志模块
│   ├── middleware          # http服务中间件
│   │   ├── common.js
│   │   ├── karma.js
│   │   ├── proxy.js
│   │   ├── runner.js
│   │   ├── source_files.js
│   │   ├── stopper.js
│   │   └── strip_host.js
│   ├── plugin.js
│   ├── preprocessor.js     # 预处理
│   ├── reporter.js         # 测试报告
│   ├── reporters
│   │   ├── base.js
│   │   ├── base_color.js
│   │   ├── dots.js
│   │   ├── dots_color.js
│   │   ├── multi.js
│   │   ├── progress.js
│   │   └── progress_color.js
│   ├── runner.js         # run命令使用
│   ├── server.js         # 主流程 Manager
│   ├── stopper.js
│   ├── temp_dir.js
│   ├── watcher.js        # 文件监控
│   └── web-server.js     # http服务
├── static
│   ├── client.html
│   ├── client_with_context.html # runInParent为false时，不用iframe
│   ├── context.html
│   ├── debug.html
│   ├── debug.js
│   └── favicon.ico

function watch(patterns, excludes, fileList, usePolling, emitter) {
  const watchedPatterns = getWatchedPatterns(patterns)
  const chokidar = require('chokidar')
  const watcher = new chokidar.FSWatcher({
    usePolling: usePolling,
    ignorePermissionErrors: true,
    ignoreInitial: true,
    ignored: createIgnore(watchedPatterns, excludes),
  })

  watchPatterns(watchedPatterns, watcher)

  watcher
    .on('add', (path) => fileList.addFile(helper.normalizeWinPath(path)))
    .on('change', (path) => fileList.changeFile(helper.normalizeWinPath(path)))
    .on('unlink', (path) => fileList.removeFile(helper.normalizeWinPath(path)))
    .on('error', log.debug.bind(log))

  emitter.on('exit', (done) => {
    watcher.close()
    done()
  })
  return watcher
}

class FileList {
  constructor(patterns, excludes, emitter, preprocess, autoWatchBatchDelay) {
    this._patterns = patterns || []
    this._excludes = excludes || []
    this._emitter = emitter
    this._preprocess = preprocess

    this.buckets = new Map()
  }

  _refresh() {
    // ... 之前代码省略
    this._patterns.map(async ({ pattern, type, nocache, isBinary }) => {
      if (helper.isUrlAbsolute(pattern)) {
        this.buckets.set(pattern, [new Url(pattern, type)])
        return
      }

      const mg = new Glob(pathLib.normalize(pattern), {
        cwd: '/',
        follow: true,
        nodir: true,
        sync: true,
      })

      const files = mg.found
        .filter((path) => {
          if (this._findExcluded(path)) {
            log.debug(`Excluded file "${path}"`)
            return false
          } else if (matchedFiles.has(path)) {
            return false
          } else {
            matchedFiles.add(path)
            return true
          }
        })
        .map((path) => new File(path, mg.statCache[path].mtime, nocache, type, isBinary))

      if (nocache) {
        log.debug(`Not preprocessing "${pattern}" due to nocache`)
      } else {
        // NOTE: preprocess
        await Promise.all(files.map((file) => this._preprocess(file)))
      }

      // NOTE: buckets用于存储build完的文件
      this.buckets.set(pattern, files)

      if (_.isEmpty(mg.found)) {
        log.warn(`Pattern "${pattern}" does not match any file.`)
      } else if (_.isEmpty(files)) {
        log.warn(`All files matched by "${pattern}" were excluded or matched by prior matchers.`)
      }
    })
    // ... 之后代码省略
  }
}

async changeFile (path, force) {
    const pattern = this._findIncluded(path)
    const file = this._findFile(path, pattern)

    if (!file) {
      log.debug(`Changed file "${path}" ignored. Does not match any file in the list.`)
      return this.files
    }

    const [stat] = await Promise.all([statAsync(path), this._refreshing])
    if (force || stat.mtime > file.mtime) {
      file.mtime = stat.mtime
      await this._preprocess(file)
      // 预处理（webpack处理） lib/preprocessor.js createPriorityPreprocessor返回的preprocess方法
      log.info(`Changed file "${path}".`)
      this._emitModified(force)
      // 发出file_list_modified事件
    }
    return this.files
    // file-list的 get files () 取出buckets中的文件
  }

const emit = () => {
  this._emitter.emit('file_list_modified', this.files)
}

function createFilesPromise(emitter, fileList) {
  // Set an empty list of files to avoid race issues with
  // file_list_modified not having been emitted yet
  let files = fileList.files
  emitter.on('file_list_modified', (filesParam) => {
    files = filesParam
  })

  return {
    then(...args) {
      return Promise.resolve(files).then(...args)
    },
  }
}

if (config.autoWatch) {
  this.on('file_list_modified', () => {
    this.log.debug('List of files has changed, trying to execute')
    if (config.restartOnFileChange) {
      socketServer.sockets.emit('stop')
      // 停止正在运行的单元测试
    }
    executor.schedule()
    // 通过socket，重新运行新一轮单元测试
  })
}

function createStopperMiddleware(urlRoot) {
  return function (request, response, next) {
    if (request.url !== urlRoot + 'stop') return next()
    response.writeHead(200)
    log.info('Stopping server')
    response.end('OK')
    process.kill(process.pid, 'SIGINT')
  }
}

;(function (window) {
  var reportTestResult = function (karma, test) {
    // 调用karma的result方法
    karma.result(result)
  }

  var createMochaReporterConstructor = function (tc, pathname) {
    return function (runner) {
      // mocha运行结束
      runner.on('test end', function (test) {
        reportTestResult(tc, test)
      })
    }
  }

  var createMochaStartFn = function (mocha) {
    // mocha启动
    return function (config) {
      mocha.run()
    }
  }

  // karma 开始测试
  window.__karma__.start = createMochaStartFn(window.mocha)
})(window)

async function runProcessors(preprocessors, file, content) {
  try {
    for (const process of preprocessors) {
      content = await executeProcessor(process, file, content)
    }
  } catch (error) {
    file.contentPath = null
    file.content = null
    throw error
  }

  file.contentPath = null
  file.content = content
  file.sha = CryptoUtils.sha1(content)
}

function setNoCacheHeaders(response) {
  response.setHeader('Cache-Control', 'no-cache')
  response.setHeader('Pragma', 'no-cache')
  response.setHeader('Expires', new Date(0).toUTCString())
}

function setHeavyCacheHeaders(response) {
  // 狠人给设置了1年的缓存。
  response.setHeader('Cache-Control', 'public, max-age=31536000')
}

socket.on('connect', function () {
  socket.io.engine.on('upgrade', function () {
    resultsBufferLimit = 1
    if (resultsBuffer.length > 0) {
      socket.emit('result', resultsBuffer)
      resultsBuffer = []
    }
  })
  var info = {
    name: navigator.userAgent,
    id: browserId,
    isSocketReconnect: socketReconnect,
  }
  if (displayName) {
    info.displayName = displayName
  }
  socket.emit('register', info)
})

{
  // 使用 IntelliSense 了解相关属性。
  // 悬停以查看现有属性的描述。
  // 欲了解更多信息，请访问: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug karma Tests",
      "type": "node",
      "request": "launch",
      "runtimeArgs": ["--inspect-brk", "${workspaceRoot}/node_modules/.bin/karma"],
      "args": [
        "start",
        "tests/unit/karma.conf.js",
        "--browsers",
        "Chrome",
        "--glob=${fileBasename}",
        "--auto-watch",
        "--reporters",
        "spec",
        "--log-level",
        "debug"
      ],
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen",
      "port": 9229
    }
  ]
}