anchor.diff:        expect(() => template.stringExpression({}), throwsA(isArgumentError));
         expect(template.stringExpression({'myvar' : id('abc')}),
                equals("'/' + (abc).map((item) => "
  -                    "common_internal.Escaper.ecapePathComponent(item))"
  +                    "commons.Escaper.ecapePathComponent(item))"
                       ".join('/')"));
       });
   
  
positive.code: 
        expect(() => template.stringExpression({}), throwsA(isArgumentError));
        expect(template.stringExpression({'My_var123' : id('abc')}),
               equals("common_internal.Escaper.ecapeVariable('\$abc')"));
      });
  
      test('path-variable-expr', () {
  
negative.code: 
        expect(() => template.stringExpression({}), throwsA(isArgumentError));
        expect(template.stringExpression({'myvar' : id('abc')}),
               equals("commons.Escaper.ecapeVariableReserved('\$abc')"));
      });
  
      test('reserved-expansion-expr', () {
  