code: function mockRequireUglify(loadError, callback) {
      var Module = require('module');
      var _resolveFilename = Module._resolveFilename;
      delete require.cache[require.resolve('uglify-js')];
      delete require.cache[require.resolve('../dist/cjs/precompiler')];
      Module._resolveFilename = function(request, mod) {
        if (request === 'uglify-js') {
          throw loadError;
        }
        return _resolveFilename.call(this, request, mod);
      };
      try {
        callback();
      } finally {
        Module._resolveFilename = _resolveFilename;
        delete require.cache[require.resolve('uglify-js')];
        delete require.cache[require.resolve('../dist/cjs/precompiler')];
      }
    }
docs: Mock the Module.prototype.require-function such that an error is thrown, when "uglify-js" is loaded.
  
  The function cleans up its mess when "callback" is finished
  
  @param {Error} loadError the error that should be thrown if uglify is loaded
  @param {function} callback a callback-function to run when the mock is active.