Validation, authentication and testing

Overview

Range, length and presence checks, looping until input is valid, simple authentication routines, normal, boundary and erroneous test data, and telling syntax errors from logic errors.

What you need to know

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Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is data validation?

   Model answer

   Validation checks that entered data follows set rules before it is accepted. Validation cannot show that data is correct, only that it is reasonable.

2. 2

   What is a range check?

   Model answer

   A range check makes sure a value lies between set limits. An example is checking that a month number is from 1 to 12.

3. 3

   What is a length check?

   Model answer

   A length check makes sure data has an acceptable number of characters. A password might have to be at least 8 characters long.

4. 4

   What is a presence check?

   Model answer

   A presence check makes sure data has been entered rather than left empty. An empty string entered for a name would be rejected.

5. 5

   How can a program keep asking until valid data is entered?

   Model answer

   The input is placed inside a loop that repeats while the data is invalid. The program only moves on once the value passes the check.

6. 6

   What does an authentication routine in a program do?

   Model answer

   An authentication routine confirms that a user is who they claim to be. A simple routine grants access only if the entered username and password match a stored pair.

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