Decision Tables A useful testing technique and more

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

In this session … ¬ Definition ¬ Application areas ¬ Steps to create a decision table ¬ Exercise ¬ Solution to exercise June 2002 2

Definition ¬ Components ¬ A decision table lists causes and effects in a matrix. Each column represents a unique combination. ¬ Purpose is to structure logic June 2002 Cause = condition Effect = action = expected results 3

Application Areas ¬ Business Analysis ¬ Programming ¬ Testing ¬ Hardware Design ¬ etc June 2002 4

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 5

Step 1: List all causes Hints: ¬ Write down the values the cause/condition can assume ¬ Cluster related causes ¬ Put the most dominating cause first ¬ Put multi valued causes last June 2002 6

Step 2: Calculate combinations Number of Values to ¬ If all causes are simply Y/N the power of the values: number of causes 2 number of causes with these values June 2002 ¬ 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 7

Step 3: Fill columns ¬ Algorithm: ¬ Determine Repeating Factor (RF): divide remaining combinations by the number of possible values for that cause ¬ Write RF times the first value, then RF times the next etc. until row is full ¬ Next row, go to 1. June 2002 8

Step 4: Reduce combinations ¬ Find indifferent combinations – place a ‘-’ ¬ Join columns where columns are identical ¬ Tip: ensure the effects are the same June 2002 9

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 June 2002 10

Step 6: Add effects to table ¬ Read column by column and determine the effects ¬ One effect can occur in multiple test combinations June 2002 11

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. June 2002 12

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? June 2002 13

Thank You June 2002 14