Testing

When first written, many programs contain . and are usually quickly removed, but it can take a long time to deduce where a lies and why. The purpose of testing is to help programmers remove such bugs and to ensure that the program functions as intended.

Test data

is that is used to test whether or not a is functioning correctly. The test data is input, the program is processed and the output is confirmed.

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

Test plans

Testing requires a . This is a list of all the tests to be used to ensure the program functions as intended. The list should include several examples of normal, boundary and erroneous data.

Tests are laid out in a test plan which might contain:

the test number
a description of what the test intends to check
the test data being used
the type of test - normal, boundary or erroneous
expected outcome
actual outcome

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

SET valid TO False WHILE valid = False DO SEND ‘Enter a number from 1 to 10’ TO DISPLAY RECEIVE number FROM (INTEGER) KEYBOARD IF number <1 OR number >10 THEN SEND ‘Number outside the range 1 to 10. Enter another number’ TO DISPLAY ELSE SET valid TO True END WHILE SEND ‘Number entered is ’, number TO DISPLAY

This program could be tested using the following normal, boundary and erroneous data:

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

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

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

Test no.	3
Description	Test the upper boundary
Test data	10
Test type	Boundary
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	Erroneous
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	Erroneous
Expected	Data is not accepted
Actual	Data is not accepted

Test plans should be created before programming starts so that they reflect all the requirements of the program design.

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

Further algorithms - EdexcelTesting

Testing

Test data

Test plans

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