Selecting and using suitable test data

Test data is that is used to test whether or not a is functioning correctly. Ideally, test data should cover a range of possible and impossible , each designed to prove a program works or to highlight any flaws. Three types of data are:

- sensible, possible data that the program should accept and be able to process
- valid data that falls at the boundary of any possible ranges
- data that the program cannot process and should not accept

Testing requires a . This is a list of all the tests that the programmer intends to use to ensure the program functions as intended. It should include several examples of valid, extreme and invalid data.

Testing tables

Tests are laid out in a testing table, which indicates:

the test number
a description of what the test intends to check
the test data being used
the type of test (valid, extreme or invalid)
expected outcome
actual outcome

Consider this simple program which asks a user to input a number from 1 to 10:

valid = FALSE
while valid == FALSE number = int(input("Enter a number from 1 to 10")) if number <1 OR number >10 then print("Number outside the range 1 to 10. Enter another number") else valid = TRUE
endwhile
print("Number entered is ", number)

This program could be tested using the following valid, extreme and invalid data:

Test no	Description	Test data	Test type	Expected	Actual
1	Test that a possible number is accepted	5	Valid	Data is accepted	Data is accepted
2	Test the lower boundary	1	Extreme	Data is accepted	Data is accepted
3	Test the upper boundary	10	Extreme	Data is accepted	Data is accepted
4	Test that the program does not accept a number less than 1	-5	Invalid	Data is not accepted	Data is not accepted
5	Test that the program does not accept a number greater than 10	20	Invalid	Data is not accepted	Data is not accepted

Test no	1
Description	Test that a possible number is accepted
Test data	5
Test type	Valid
Expected	Data is accepted
Actual	Data is accepted

Test no	2
Description	Test the lower boundary
Test data	1
Test type	Extreme
Expected	Data is accepted
Actual	Data is accepted

Test no	3
Description	Test the upper boundary
Test data	10
Test type	Extreme
Expected	Data is accepted
Actual	Data is accepted

Test no	4
Description	Test that the program does not accept a number less than 1
Test data	-5
Test type	Invalid
Expected	Data is not accepted
Actual	Data is not accepted

Test no	5
Description	Test that the program does not accept a number greater than 10
Test data	20
Test type	Invalid
Expected	Data is not accepted
Actual	Data is not accepted

Ideally, a programmer should run as many tests as is sensible. Many large programs, especially games, contain simply because it may not be possible to test every possible input or action.

Refining algorithms

After an algorithm has been tested, it may need to be refined to improve how it works and to make it efficient. This is a part of the testing life cycle. Refining an algorithm helps to ensure that it is as good as it can be, before being used in a live and active system. Refining an algorithm requires changes that:

fix problems that are found during testing
make the algorithm more efficient by reducing any unnecessary or repetitive steps
improving readability and maintainability so that others can understand the algorithm.

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Producing robust programs - OCRSelecting and using suitable test data