text: import os
  
  SYSTEM_FILES = set(
          ('_pyjs.js',
           'bootstrap.js',
          )
          )
  
  def outputContainsSystemFiles(outputDir):
      dirs = set(os.listdir(outputDir))
      assert dirs & SYSTEM_FILES == SYSTEM_FILES
  
  def outputContainsPlatforms(outputDir, moduleName, platforms):
      platformFiles = ['%s.%s.cache.html'% (moduleName, p) for p in platforms]
      outputContainsFiles(outputDir, platformFiles)
  
  def outputContainsFiles(outputDir, fileNames):
      dirs = set(os.listdir(outputDir))
      fileNames = set(fileNames)
      assert dirs & fileNames == fileNames
  
  
  