Posts Tagged ‘decision tables’

Super simple method to create a boolean decision table

Posted in software development, testing on March 27th, 2009 by Joerg – 3 Comments

Today one of our test engineers, Manfred, presented about systematic identification of test values. One of the topics were decision tables. I was fascinated how easy he created tables with all possible combinations. Here is how:

  1. Write the conditions in seperate rows.
    2. Condition A
Condition B
Condition C
  2. Now make 2^n columns where n is the number of conditions.
    3. Condition A |   |   |   |   |   |   |   |   |
Condition B |   |   |   |   |   |   |   |   |
Condition C |   |   |   |   |   |   |   |   |
  3. Start at the bottom condition and write alternating Y and N.
    4. Condition A |   |   |   |   |   |   |   |   |
Condition B |   |   |   |   |   |   |   |   |
Condition C | Y | N | Y | N | Y | N | Y | N |
  4. Fill the next row with alternating Y Y N N …
    5. Condition A |   |   |   |   |   |   |   |   |
Condition B | Y | Y | N | N | Y | Y | N | N |
Condition C | Y | N | Y | N | Y | N | Y | N |
  5. Each row you double the number of consecutive Ys and Ns.
    6. Condition A | Y | Y | Y | Y | N | N | N | N |
Condition B | Y | Y | N | N | Y | Y | N | N |
Condition C | Y | N | Y | N | Y | N | Y | N |
  6. Do so until all rows are filled.
  7. Now you can add your decisions to the table.
    8. Condition A | Y | Y | Y | Y | N | N | N | N |
Condition B | Y | Y | N | N | Y | Y | N | N |
Condition C | Y | N | Y | N | Y | N | Y | N |
---------------------------------------------
Decision 1  |   | X | X |   |   |   |   |   |
...

Using this algorithm you can be sure you covered all combinations. It doesn’t matter how many conditions you have and you don’t even have to think :)

Thanks Manfred!