Testing Algorithms (AQA GCSE Computer Science)

Testing Algorithms

What is the purpose of testing algorithms?

• Testing is carried out for many reasons, however, 4 main areas are:

  • To ensure there are no errors or bugs in the code

  • To ensure that the code performs as it was intended

  • To ensure no one can gain unauthorised access to the system

  • To check the program solves the initial problem and meets all requirements

What are the different types of testing?

• There are two types of tests that developers and teams will do to ensure their programs are robust and meet the requirements that have been set out, they are: 

  • Iterative testing

  • Final testing

Iterative Testing

• Each part of a program is tested

• Every pathway through the program is tested

  • This includes each branch/pathway inside of IF statements

• This is done during the development of the program

• Iterative testing means repeatedly testing the program whilst continuing to make changes and make improvements

• This method of testing ensures that the program is fully functional and working as intended

Final Testing

• Testing that all parts (modules) of a program work together

• Checking the program against real data to ensure it meets all of the requirements

  • Testing the program using normal, boundary and erroneous data

• Final testing is done towards the end of the development cycle, once the entire program is complete

• Final testing can include

  • Alpha testing

  • Beta testing

Normal, Boundary & Erroneous Tests

Categories of tests

• The are three main categories of tests a programmer or test-user would carry out whilst performing both iterative or final testing on a program

  • Normal tests

  • Boundary tests

  • Erroneous tests

• There is an additional test that users would always carry out to test the robustness of their program, this is known as an invalid test

• To explain the types of tests, some example code will be used

Example code

# Ask for user's name
name = input("What is your name? ")

# Ask for user's age
age = int(input("How old are you? "))

# Check if age is between 12 and 18
if age >= 12 and age <= 18:
    print("Welcome, " + name + "! Your age is accepted.")
else:
    print("Sorry, " + name + ". Your age is not accepted.")

Normal tests

• A normal test is when a user enters data that should be accepted in the program

• An example would be a user entering their age as 16 into the age field of the program

Boundary tests

• A boundary test is when a user enters data that is on the edge of what is acceptable 

• An example would be a user entering their age as 12 or 18 into the age field of the program

• Another example of a boundary test would be the numbers 11 or 19, even though they are outside of the accepted range

Erroneous tests

• An erroneous test is when a user enters data that is the wrong data type

• An example would be a user entering their age as "F" into the age field of the program

Invalid tests

• An invalid test is when a user enters data that is the right data type but it is outside of what is accepted

• An example would be a user entering their age as 67 into the age field of the program

Selecting Suitable Test Data

How do you select and justify suitable test data?

• The first step when selecting suitable test data is to determine what type of input is expected from a user

• In the example table below, a user is expected to enter a number between 12 and 18

• Suitable checks include

  • The numbers between 12 and 18

  • Numbers outside of this range

  • Incorrect data types

• Examples of each the the above have been summarised in the table below