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Decision Tables

A useful testing technique and

more

Marien de Wilde, Solution Architect

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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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Application Areas

Business Analysis

Programming

Testing

Hardware Design

etc

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Steps to Create a decision table

1. List all causes in the decision table

2. Calculate the number of possible

combinations3. Fill columns with all possible

combinations

4. Reduce test combinations5. Check covered combinations

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* 2 3= 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 indifferent

combinations place

a -

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 effects

are 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. 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.

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Solution on next slide

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Exercise: possible solution

2 or more current lines ORcredit 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