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Decision Tables A useful testing technique and more… Marien de Wilde, Solution Architect

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February In this session … Definition Application areas Steps to create a decision table Exercise Solution to exercise

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

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February Application Areas Business Analysis Programming Testing Hardware Design etc

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February 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

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February 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

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February Step 2: Calculate combinations If all causes are simply Y/N values: 2 number of causes If 1 cause with 3 values and 3 with 2: 3 1 * 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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February Step 3: Fill columns Algorithm: 1. Determine Repeating Factor (RF): divide remaining combinations by the number 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.

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February Step 4: Reduce combinations Find indifferent combinations – place a - Join columns where columns are identical Tip: ensure the effects are the same

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February 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

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

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February 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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February Solution on next slide

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February 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?

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February Thank You

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