Suitable Test Data (Cambridge (CIE) O Level Computer Science)

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Robert Hampton

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Computer Science Content Creator

Suitable Test Data

What is suitable test data?

Suitable test data is specially chosen to test the functionality of a program or design
Developers or test-users would pick a selection of test data from the following categories
- Normal
- Abnormal
- Extreme
- Boundary
The results would be compared to the expected results to check if the algorithm/program works as intended
Each category is explained within the context of a simple Python program below, comments have been added to help explain the processes

Python
# 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.")`

Python

# 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 data

Normal test data is 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

Abnormal data

Abnormal test data is 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

Extreme data

Extreme test data is the maximum and minimum values of normal data that are accepted by the system
An example would be a user entering their age as 18 or 12 into the age field of the program

Boundary data

Boundary test data is similar to extreme data except that the values on either side of the maximum and minimum values are tested
The largest and smallest acceptable value is tested as well as the largest and smallest unacceptable value
An example would be a user entering their age as 11 or 19 into the age field of the program

Selecting suitable test data

Type of Test	Input	Expected Output
Normal	14	Accepted
Normal	16	Accepted
Extreme	12	Accepted
Extreme	18	Accepted
Abnormal	H	Rejected
Abnormal	@	Rejected
Boundary	11	Rejected
Boundary	19	Rejected

Worked Example

A programmer has written an algorithm to check that prices are less than $10.00

These values are used as test data: 10.00 9.99 ten

State why each value was chosen as test data.

[3]

Answers

10.00 is boundary or abnormal data and should be rejected as it is out of range [1]

9.99 is boundary, extreme and normal data and should be accepted as it is within the normal range [1]

Ten is abnormal data and should be rejected as it is the wrong value type [1]

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