decision+table+training+ a+useful+testing+technique
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Decision Tables
A useful testing technique and
more…
Marien de Wilde, Project Manager
IBM New Zealand Ltd, 021 - 474 018
© Copyright IBM New Zealand Ltd, June 2002
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June 2002 2
In this session …
Definition
Application areas
Steps to create a
decision table
ExerciseSolution to exercise
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Definition
Components
A decision table lists
causes and effects in amatrix. Each column
represents a unique
combination.
Purpose is to structure
logic
Cause = condition
Effect = action = expected results
Causes Values 1 2 3 4 5 6 7 8
Cause 1 Y, N Y Y Y Y N N N N
Cause 2 Y, N Y Y N N Y Y N N
Cause 3 Y, N Y N Y N Y N Y N
Effects
Effect 1 X X X
Effect 2 X X X
Combinations
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June 2002 4
Application Areas
Business Analysis
Programming
Testing
Hardware Design
etc
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Steps to Create a decision table
1. 1. List all causes in the decision
table
2. 2. Calculate the number of possible combinations
3. 3. Fill columns with all possible
combinations
4. 4. Reduce test combinations
5. 5. Check covered combinations
6. 6. Add effects to the table
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Step 1: List all causes
Hints:
Write down the values
the cause/conditioncan assume
Cluster related causes
Put the mostdominating cause first
Put multi valued
causes last
Causes Values 1 2 3
Cause 1 Y, N Y Y Y
Cause 2 Y, N Y Y N
Cause 3 Y, N Y N Y
Effects
Effect 1 X
Effect 2 X
Com
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Step 2: Calculate combinations
If all causes are simply Y/N
values:
2number of causes
If 1 cause with 3 values and 3
with 2:
31 * 23 = 24
Or, use the Values column
and multiply each value
down the column, eg.
3*2*2*2=24
Number of Values to
the power of the
number of causes
with these values
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Step 3: Fill columns
Algorithm:
1. Determine Repeating Factor (RF):
divide remaining combinations by thenumber of possible values for that
cause
2. Write RF times the first value, then
RF times the next etc. until row is full
3. Next row, go to 1.
s Values 1 2 3 4 5 6 7 8
1 Y, N Y Y Y Y N N N N
2 Y, N Y Y N N Y Y N N
3 Y, N Y N Y N Y N Y N
s
t 1 X X X
t 2 X X X
Combinations
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Step 4: Reduce combinations
Find indifferentcombinations – placea „-‟
Causes Values 1 2 3 4 5 6 7 8
Cause 1 Y, N Y Y Y Y N N N N
Cause 2 Y, N Y Y N N Y Y N N
Cause 3 Y, N Y N - - Y N Y NEffects
Effect 1 X X X
Effect 2 X X X
Combinations
Causes Values 1 2 3 4 5 6 7
Cause 1 Y, N Y Y Y N N N N
Cause 2 Y, N Y Y N Y Y N N
Cause 3 Y, N Y N - Y N Y N
Effects
Effect 1 X X
Effect 2 X X X
Combinations
Join columns wherecolumns are identical
Tip: ensure the effectsare the same
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Step 5: Check covered
combinations
Checksum
For each column calculate the
combinations it represents
A „-‟ represents as many
combinations as the cause has
Multiply for each „-‟ down the
column
Add up total and compare with
step 2
Causes Values 1 2 3 4
Cause 1 Y, N Y Y Y N
Cause 2 Y, N Y N N -
Cause 3 Y, N - Y N -
Effects
Effect 1 X X
Effect 2
Checksum 2 1 1 4 8
Combinations
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Step 6: Add effects to table
Read column by
column and determine
the effectsOne effect can occur
in multiple test
combinations
Causes Values 1 2 3 4
Cause 1 Y, N Y Y Y N
Cause 2 Y, N Y N N -
Cause 3 Y, N - Y N -
Effects
Effect 1 X X
Effect 2 X X
Checksum 2 1 1 4 8
Combinations
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Exercise: Specification
Create a decision table
A mailing is to be sent out to customers. Thecontent of the mailing is about the current levelof discounting and potential levels of discounting. The content is different for differenttypes of customers.
Customer Types A, B and C get a normal letter except Customer Type C, who get a special letter.Any customer with 2 or more current lines or with a credit rating of „X‟ get a special paragraphadded with an offer to subscribe to another levelof discounting.
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Exercise: possible solution
“2 or more current lines OR credit rating X”. What if both: AND?
Other customer types? See “O-Other” above.
What about non current lines?
Causes Values 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Customer Type A,B,C,O A A A A B B B B C C C C O O O O
2 or more lines Y, N Y Y N N Y Y N N Y Y N N Y Y N N
Credit rating = X Y, N Y N Y N Y N Y N Y N Y N Y N Y NEffects
Normal Letter X X X X X X X X ? ? ? ?
Special Letter X X X X ? ? ? ?
Add. Paragraph ? X X ? X X ? X X ? ? ? ?
No Letter ? ? ? ?
Checksum 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 16
Combinations
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Thank You