Decision Table Training Session
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Transcript of Decision Table Training Session
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
June 2002 2
In this session …
DefinitionApplication areasSteps to create a
decision tableExerciseSolution to exercise
June 2002 3
Definition
ComponentsA decision table lists
causes and effects in a matrix. Each column represents a unique combination.
Purpose is to structure logic
Cause = conditionEffect = action = expected results
Causes Values 1 2 3 4 5 6 7 8Cause 1 Y, N Y Y Y Y N N N NCause 2 Y, N Y Y N N Y Y N NCause 3 Y, N Y N Y N Y N Y NEffectsEffect 1 X X XEffect 2 X X X
Combinations
June 2002 4
Application Areas
Business AnalysisProgrammingTestingHardware Design etc
June 2002 5
Steps to Create a decision table
1. List all causes in the decision table
2. Calculate the number of possible combinations
3. Fill columns with all possible combinations
4. Reduce test combinations 5. Check covered combinations 6. Add effects to the table
June 2002 6
Step 1: List all causes
Hints:Write down the values
the cause/condition can assume
Cluster related causesPut the most
dominating cause firstPut multi valued
causes last
Causes Values 1 2 3 4 5 6 7 8Cause 1 Y, N Y Y Y Y N N N NCause 2 Y, N Y Y N N Y Y N NCause 3 Y, N Y N Y N Y N Y NEffectsEffect 1 X X XEffect 2 X X X
Combinations
June 2002 7
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
June 2002 8
Step 3: Fill columns
1. Algorithm:
2. Determine Repeating Factor (RF): divide remaining combinations by the number of possible values for that cause
3. Write RF times the first value, then RF times the next etc. until row is full
4. Next row, go to 1.
June 2002 9
Step 4: Reduce combinations
Find indifferent combinations – place a ‘-’
Causes Values 1 2 3 4 5 6 7 8Cause 1 Y, N Y Y Y Y N N N NCause 2 Y, N Y Y N N Y Y N NCause 3 Y, N Y N - - Y N Y NEffectsEffect 1 X X XEffect 2 X X X
Combinations
Causes Values 1 2 3 4 5 6 7Cause 1 Y, N Y Y Y N N N NCause 2 Y, N Y Y N Y Y N NCause 3 Y, N Y N - Y N Y NEffectsEffect 1 X XEffect 2 X X X
Combinations Join columns where
columns are identicalTip: ensure the effects are
the same
June 2002 10
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 4Cause 1 Y, N Y Y Y NCause 2 Y, N Y N N -Cause 3 Y, N - Y N -EffectsEffect 1 X XEffect 2Checksum 2 1 1 4 8
Combinations
June 2002 11
Step 6: Add effects to table
Read column by column and determine the effects
One effect can occur in multiple test combinations
Causes Values 1 2 3 4Cause 1 Y, N Y Y Y NCause 2 Y, N Y N N -Cause 3 Y, N - Y N -EffectsEffect 1 X XEffect 2 X XChecksum 2 1 1 4 8
Combinations
June 2002 12
Exercise: SpecificationCreate a decision table
A mailing is to be sent out to customers. The content of the mailing is about the current level of discounting and potential levels of discounting. The content is different for different types 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 paragraph added with an offer to subscribe to another level of discounting.
June 2002 13
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 16Customer Type A,B,C,O A A A A B B B B C C C C O O O O2 or more lines Y, N Y Y N N Y Y N N Y Y N N Y Y N NCredit rating = X Y, N Y N Y N Y N Y N Y N Y N Y N Y NEffectsNormal 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
June 2002 14
Thank You