anchor.diff:        return;
       }
   
  -    //TODO vector
  +    if (type == EvaluationType.VECTOR) {
  +      //TODO vector
  +    }
     }
   
     /// Test the constructors of expressions.
  
positive.code:   get testFunctions => {
      'Expression Creation [REAL]': simpleRealCreation,
      'Expression Creation [INTERVAL]': simpleIntervalCreation,
      'Expression Creation [VECTOR]': simpleVectorCreation,
      'Binary Op Convenience Creation': convenienceBinaryCreation,
      'Unary Op Convenience Creation': convenienceUnaryCreation,
      'Operator simplification': baseOperatorSimplification,
      'Operator differentiation': baseOperatorSimplification,
      'Simple evaluation [REAL]': simpleRealEval,
      'Simple evaluation [INTERVAL]': simpleIntervalEval,
      'Simple evaluation [VECTOR]': simpleVectorEval,
      'Default Function Creation': defFuncCreation,
      'Default Function simplification': defFuncSimplification,
      'Default Function differentiation': defFuncDifferentiation,
      'Default Function evaluation [REAL]': defFuncRealEval,
      'Default Function evaluation [INTERVAL]': defFuncIntervalEval,
      'Default Function evaluation [VECTOR]': defFuncVectorEval,
      'Custom Function Creation': cusFuncCreation,
      'Custom Function simplification': cusFuncSimplification,
      'Custom Function differentiation': cusFuncDifferentiation,
  
negative.code:     'Composite Function simplification': compFuncSimplification,
      'Composite Function differentiation': compFuncDifferentiation,
      'Composite Function evaluation': compFunEval
      */
    };
  
    void initTests() {
  