Challenges

When you’ve finished writing the basic version of the program, try tackling some additional challenges:

• Ensure that the user can enter only numbers for the bill amount and the tip rate. If the user enters non-numeric values, display an appropriate message and exit the program. Here’s a test plan as an example:

  ​	Input:
  ​	bill amount: abcd
  ​	tip rate: 15
  ​	Expected result: Please enter a valid number for
  ​	the bill amount.

• Instead of displaying an error message and exiting the program, keep asking the user for correct input until it is provided.

• Don’t allow the user to enter a negative number.

• Break the program into functions that do the computations.

• Implement this program as a GUI program that automatically updates the values when any value changes.

• Instead of the user entering the value of the tip as a percentage, have the user drag a slider that rates satisfaction with the server, using a range between 5% and 20%.