Abdisalam Issa-Salwe, Thames Valley University 3 Decision table A decision table is a tabular representation for conditional action. It was developed as a design technique for complicated decisions. The first half of a decision table specifies possible combinations of conditions; the second half arranged below the first, specifies the actions taken for each combination. The first half are guards for actions in the second half.

1. 1
Quality Assurance
and
Testing
(2)
Lecture 17
Abdisalam Issa-Salwe
Thames Valley University

2. Abdisalam Issa-Salwe, Thames Valley University
2
Topic list
 Testing methods of testing
 Developing a testing strategy

3. Abdisalam Issa-Salwe, Thames Valley University
3
Decision table
 A decision table is a tabular
representation for conditional action.
It was developed as a design
technique for complicated decisions.
 The first half of a decision table
specifies possible combinations of
conditions; the second half arranged
below the first, specifies the actions
taken for each combination.
 The first half are guards for actions in
the second half.

4. Abdisalam Issa-Salwe, Thames Valley University
4
Decision table (cont...)
 This technique works well for a few,
strongly interrelated conditions and
actions. It makes information easy to
determine but sequence information is
implicit.
 Decision tables and decision trees help
us consider all the possible actions
that need be taken under a given set
of circumstances in a complete and
unambiguous fashion.

5. Abdisalam Issa-Salwe, Thames Valley University
5
Decision table (cont...)
 To design a decision table:
 Specify the name of the table as its
heading, and insert a reference to it
at the place in the process
description where the table applies
 List all possible conditions in the
condition stub
 List all possible actions in the action
stub

6. Abdisalam Issa-Salwe, Thames Valley University
6
Decision table (cont...)
 Fill in the condition entries by marking
the presence (Y) or absence (N) of the
conditions. The number of rules, that
is, entries in the right-hand side of the
table equals the number of possible
combinations of conditions.
 For every condition entry, mark with
an X an action entry opposite the
action(s) to be taken under these
circumstances.

7. Abdisalam Issa-Salwe, Thames Valley University
7
Decision table (cont...)
 Characteristics of decision trees
 They are easier to read than are
decision tables, but the greater
the number of conditions, the
more tedious they are to draw
up.
 They are better for checking the
completeness of the policy
represented.

8. Abdisalam Issa-Salwe, Thames Valley University
8
Conditions
Is it 8 o’clock yet?
Is it the weekend?
Entry
Yes
No
Actions
Get up
Stay in bed
Entry
X

9. Abdisalam Issa-Salwe, Thames Valley University
9
Conditions
Is it 8 o’clock yet?
Is it the weekend?
Entry
Yes
No
Actions
Get up
Stay in bed
Entry
X

10. Abdisalam Issa-Salwe, Thames Valley University
10
Conditions
Is it 8 o’clock yet?
Is it the weekend?
1 2 3 4
Actions
Get up
Stay in bed

11. Abdisalam Issa-Salwe, Thames Valley University
11
Conditions
Is it 8 o’clock yet?
Is it the weekend?
1 2 3 4
Y Y N N
Y N Y N
Actions
Get up
Stay in bed

12. Abdisalam Issa-Salwe, Thames Valley University
12
Conditions
Is it 8 o’clock yet?
Is it the weekend?
1 2 3 4
Y Y N N
Y N Y N
Actions
Get up
Stay in bed
X
X
X X

13. Abdisalam Issa-Salwe, Thames Valley University
13
Decision table (cont...)
 Advantages:
 Information is presented through a table
in an easy to modify format. Decision
table systems correspond with known
design techniques.
 Disadvantages
 Sequence information is implicit

14. Abdisalam Issa-Salwe, Thames Valley University
14
Developing testing strategy
 Strategy approach
 To be formulated that the details approach
that will be taken to testing, including the
tests to be conducted and the testing
tools/techniques that will be used
 Test plan:
 A test plan should be developed that
state:
 What will be tested
 When it will be tested (sequence)
 The test environment

15. Abdisalam Issa-Salwe, Thames Valley University
15
Limitation
 Poor testing process:
 The test plan may not cover all area of
system functionality
 Inadequate time:
 Software and systems are inevitable
produces under significant time pressure
 Future requirements not anticipated:
 The test data used may have been fine at
the time of testing, but future demands
may be outside the range of values tested

16. Abdisalam Issa-Salwe, Thames Valley University
16
Limitation (cont…)
 Software changes inadequate tested:
 System/software changes made as a
result of testing findings or for other
reasons may not be adequately tested as
they were not in the original test plan