Testing Methods for systems

1. 1
System Testing
Bernie Fishpool
Testing Methodologies

2. 2
Strategies
 Top down
 Skeleton of system is completed
 Individual models replaced by
stubs displaying messages
 As modules completed they are
embedded into the system
skeleton and tested

3. 3
Strategies
 Bottom up
 Individual modules tested in a
stand-alone fashion
 Individual modules combined into
larger units and tested together
 Full system test

4. 4
Planning Testing
 Good testing requires:
 A thorough knowledge and
understanding of what the system
is supposed to do
 Preparation of ‘expected results’ to
be used in testing activities
 Identification of system limits
 Creation of test data

5. 5
Objectives of testing
 Does the logic work properly?
 Does the system work as
intended?
 Can system be made to crash?
 Is all necessary logic present?
 Is any functionality missing?
 Does system do everything
specified?

6. 6
Functional Testing
(Black Box Testing)
 Carried out independently of the
system
 Involves looking at the systems
specification and creating test data
that covers all inputs and outputs
of the function

7. 7
Logical Testing (White
Box Testing)
 Testing the logic of the system
 Involves studying the system to
attempt to test each logic path at
least once
 e.g. Testing an IF statement in a
program or testing validation rule in
a database

8. 8
Problems
 Black box testing does not test all
logical paths in a system unless
sufficient test data is created
(which is often not easy to identify)
 White box testing does not detect
missing functions because you can
not test what is not there!

9. 9
Whole System Testing
 WARNING!
Testing may take up to as much as
50% of development time

10. 10
Test Plan
You should consider:
Purpose of test
Objectives and what part of system
is being tested
Location and timing
Where and when

11. 11
Test description
What the inputs are and what the
expected outputs are
Test procedure
How test data is prepared
How output results will be captured
How results will be analysed
Test Plan

12. 12
Testing for Recovery
 Test to ensure that system can
recover from various types of
failure
 This is important in real-time
systems controlling physical
devices or in large on-line
databases
 Simulation of hardware and power
failures

13. 13
Testing for Performance
 Testing that system can handle
volumes of data expected in user
environment

14. 14
Test Data
 3 categories of test data
 Normal data defined as most general
data that the system was designed to
handle
 Extreme data defined as valid data
tested at upper and lower limits of
acceptability (boundary testing)
 Exceptional data defined as data
which the system is capable of detecting
and rejecting

15. 15
Designing Test Data
 Live data testing
 Tester selects examples of live
data from the system which fulfil
the conditions to be tested
 Manual calculations are
undertaken
 Results compared

16. 16
Designing Test Data
 Historical data
 Sampling of transactions that have
already taken place
 These transactions are then
passed through the system
 Results compared

17. 17
Designing Test Data
 Dummy test data
 Fictitious data created to test conditions
 Creation of dummy files specifically for
testing purposes
 Useful for:
 Validating data preparation procedures
 Validation controls
 Computational and logical processes

18. 18
Ensure that:
 All system outputs are tested
 Information produced is accurate
 Information produced is realistic
and has value