anchor.diff:      eval = e2.evaluate(interval, cm);
       expect(eval, equals(int1 / int2));
   
  +    //TODO
   //    eval = e3.evaluate(interval, cm);
   //    expect(eval, equals(i1 ^ i2));
   
  
positive.code:     expect(_hasMember(e6, n1), isTrue);
    }
  
    void simpleIntervalCreation() {
      _createBasicExpressions(interval);
  
  
negative.code:   void defFuncCreation() {
      // Create all the default functions:
      // Log, Ln, Cos, Sin, Tan, Pow, etc.
     
      // Test with number literal
      Expression exp = n2;
      List<MathFunction> functions = _createDefaultFunctions(n2);
      
      for (MathFunction fun in functions) {
        // Numbers get boxed into BoundVariable, check for those instead of contains
        expect(fun.args, anyElement(new isInstanceOf<BoundVariable>()));
      }
      
      // Test with variable
      exp = new Variable('x');
      functions = _createDefaultFunctions(exp);
      
      for (MathFunction fun in functions) {
        // Variables should not get boxed, test for contains
        expect(fun.args, contains(exp));
      }
    }
    
    List<MathFunction> _createDefaultFunctions(Expression exp) {
      return [new Cos(exp),
              new Exponential(exp),
              new Log(exp, exp),
              new Ln(exp),
              new Root(5, exp),
              new Root.sqrt(exp),
              new Sqrt(exp),
              new Sin(exp),
              new Tan(exp)];
    }
  
    void defFuncRealEval() {
  