@Test(expected = MalformedExpressionException.class)
  public void evalExceptOnNoArguments() throws MalformedExpressionException {
    String operationExpression = "-";

    PostfixEvaluator testPostfix = new PostfixEvaluator(operationExpression);

    try {
      testPostfix.eval();
    } catch (Exception e) {
      throw e;
    }
  }
 /**
  * Create a PostfixEvaluator on the given sequence of operations, and return the results of
  * eval(), or catches an exception thrown by eval().
  *
  * @param operationExpression the sequence of operations to perform, written in RPN or postfix
  *     notation.
  * @return the results of running PostfixEvaluator.eval() on the operationExpression.
  */
 private double evalTest(String operationExpression) {
   PostfixEvaluator testPostfix = new PostfixEvaluator(operationExpression);
   double evalResult = 0;
   try {
     evalResult = testPostfix.eval();
   } catch (Exception e) {
     System.out.println("Unexpected exception occurred. Details:");
     System.out.println("\t" + e.getClass());
     System.out.println("\t" + e.getMessage());
   }
   return evalResult;
 }