2. Testing
Testing begins at the analysis and design stages,
with prototypes being developed
It is much more cost effective to fix problems at
earlier stages of the software development process
3. Testing
The purpose of testing is to
to identify errors
to ensure that software is fit for purpose
to ensure that code is efficient
to ensure that code is maintainable
4. Test plan
Selecting appropriate test data sets is important, so we
need to create a test plan
Expected results should be known in advance (so the
actual output can be checked against expected output)
6. Test Data Sets
Normal Data
A normal data set should be tested to show that the
program works as expected.
7. Test Data Sets
Extreme Data
Extreme data is used to test the boundary limits within
a program.
8. Test Data Sets
Exceptional Data
Exceptional data is used to test that the program can
properly handle unexpected inputs.
9. Comprehensive testing
Software should undergo comprehensive testing
This means testing against a range of normal,
exceptional and extreme data
It does not mean running a program a couple of times
to find that it works OK.
10. Phases of testing
1. Procedure / Module Testing
Individual code procedures and modules tested
2. Integration Testing
Test the modules work together
3. System Testing
Test overall system
4. Acceptance Testing
Customer tests program against their specification
5. Alpha and Beta Testing
Put the software out to users to test
11. Who tests?
Initially, tests are carried out by the development team
Acceptance testing is carried out by the client
The final alpha and beta test are carried out by a select
band of users. It is becoming common for software beta
programs to be freely downloadable
12. Syntax Errors
Syntax errors are errors which appear in your code
and can be misspelled keywords or using the
language incorrectly
Often software development environments will
highlight syntax errors for you
Syntax errors are the most common type of errors
16. Logic Errors
Logic errors are those that appear when the program
is running
They will not cause the program to crash but will
produce unwanted or unexpected results
19. Dry Runs
Stepping through each line of the program code,
manually working out on the values of variables in a
table
The tester/developer works as the computer
20. Trace Table
A trace table is used to store the current value of
each variable as the programmer steps through the
dry run program line by line
21. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
22. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
23. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
24. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
25. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
26. Trace Table
SET savings TO 60
SET pocket_money TO 10
REPEAT WITH month FROM 1 to 4
SET savings TO savings + pocket_money
END REPEAT
27. Breakpoints
A breakpoint is used to stop a program at a
particular line of code
The programmer can then examine the value of
variables at this point
Can also then step through subsequent lines of code
one at a time
28. Breakpoints
In this example, a breakpoint has been added to test
whether or not the code within the IF statement is actually
run
We can see it has. We can also check the state of
variables
29. Testing removes all bugs...
...wrong!
Testing can only convince us of the presence of errors,
and not of their absence.
Testing can never prove conclusively that a program is
correct. No matter how exhaustive the testing, it will
always be possible for the system to contain errors
which have not been detected.
