There are three reasons for testing:

1. To test that the system works under normal data.
2. To test that the system works with extreme data.
3. To test the response if erroneous or incorrect data is entered.

The easy way to remember this is to test VALID, INVALID AND EXTREME DATA

When testing, it is common to use a test plan an example is shown below

• Include tests for valid data​
  
  
• Include tests for invalid or erroneous data​
  
  
• Include tests for extreme data​
  
  
• Use a test plan​
  
  
• Get other students to try and ‘break’ your solution​
  
  
• Include evidence​
  
  
• Refer to the type of error