old_contents: var expect = require('chai').expect;
  var
    Transformer = require('./../../lib/transformer'),
    transformer = new Transformer({
      formatter: false,
      transformers:{
        generateExport:false
      }
    });
  
  function test(script) {
    transformer.read(script);
    transformer.applyTransformations();
    return transformer.out();
  }
  
  describe('Comments', function () {
  
    it("shouldn't convert comment line", function (done) {
      var script = '// comment line\nvar x = 42;';
  
      expect(test(script)).to.equal('// comment line\nconst x = 42;');
      done();
    });
  
    it("shouldn't convert trailing comment", function (done) {
      var script = 'var x = 42;    // trailing comment\n';
  
      expect(test(script)).to.equal('const x = 42;    // trailing comment\n');
      done();
    });
  
  });
  
new_contents: var expect = require('chai').expect;
  var
    Transformer = require('./../../lib/transformer'),
    transformer = new Transformer({
      formatter: false,
      transformers:{
        generateExport:false
      }
    });
  
  function test(script) {
    transformer.read(script);
    transformer.applyTransformations();
    return transformer.out();
  }
  
  describe('Comments', function () {
  
    it("shouldn't convert comment line", function (done) {
      var script = '// comment line\nvar x = 42;';
  
      expect(test(script)).to.equal('// comment line\nconst x = 42;');
      done();
    });
  
    it("should remove trailing comment", function (done) {
      var script = 'var x = 42;    // trailing comment\n';
  
      expect(test(script)).to.equal('const x = 42;');
      done();
    });
  
  });
  
subject: Fix unit test