Swe3643 2006 Decision Table Based TestingPresentation Transcript
Decision Table Based Testing
Decision table is based on logical relationships just as the truth table.
Decision Table is a tool that helps us look at the combination of conditions
Completeness of conditions
Inconsistency of conditions
Components of a Decision Table C1 C2 C3 a1 a2 a3 a4 a5 T T T T F F F F T T F F T T F F T F T F T F T F x x x x x x x x x x x x x x conditions actions values of conditions actions taken R1 R2 R3 R4 R5 R6 R7 R8 rules Read a Decision Table by columns of rules : R1 says when all conditions are T, then actions a1, a2, and a5 occur
Conditions in Decision Table
The conditions in the decision table may take on any number of values . When it is binary , then the decision table conditions are just like a truth table set of conditions.
The decision table allows the iteration of all the combinations of values of the condition, thus it provides a “completeness check.”
The conditions in the decision table may be interpreted as the inputs of the table , and the actions may be thought of as outputs of the table .
How do you decide how many rules must exist ----- use this to check against Requirements Doc.?
While you get the conditions from the requirement statements, what exactly do you look for?
Requirement statement that talks about inputs
Requirement statement that talks about processing
Requirement statement that talks about outputs
Requirement statement that talks about criteria
Triangle Problem Example (“short” form)
a < b + c
b < a + c
c < a + b
a = b
a = c
b = c
F T T T T T T T T T T - F T T T T T T T T T - - F T T T T T T T T - - - T T T T F F F F - - - T T F F T T F F - - - T F T F T F T F X X X X X X X X X X X Note the Impossible cases Pick input set, <a, b, c>, for each of the columns, or rules, below Assume a, b and c are all between 1 and 200 R1 R2 R3 R4 R5 R7 R6 R9 R8 R11 R10 Explain?
How Many Test Cases for Triangle Problem?
There is the “invalid” situation --- Not a Triangle :
There are 3 test conditions in the Decision table
Note the “-” entries, which represents “don’t care,” when it is determined that the input sides <a, b, c> do not form a triangle
There is the “valid” situation ---- A Triangle :
There are 3 types of valid; so there are 2 3 = 8 test conditions
But there are 3 “impossible” situations
So there are only 8 – 3 = 5 test conditions
So, for valid values of a, b, and c, we need to come up with 8 sets of <a, b, c> to test the ( 3 + 5 ) = 8 test conditions .
Also, note that as we logically thought through this, it made us “look at’ the Requirement statement s more carefully.
Calendar Next-Date Problem
The Calendar next-date problem has many constraints, one of which deals with the value of the month:
Condition 1 : 1 <= month <= 12
Condition 2 : month < 1
Condition 3 : month > 12
A Decision Table for Next-Date Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F There are 2 3 = 8 test conditions (8 columns) for the month value. But ------- are these really “independent” conditions ?
Decision Table for Next-Date Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F Remember : Condition 1: 1 < = m <= 12 Condition 2: m < 1 Condition 3: m > 12 R1 R2 R3 R4 R5 R6 R7 R8 Note that: a) If condition 1 is true, then conditions 2 and 3 must both be false. So Rules 1 – 4 is reduced to just R4. b) If condition 1 is false, then only one of the conditions 2 / 3, not both, can be true. So, rule R5 can be eliminated. c) Not all three conditions can be false. So rule R8 can be eliminated. That leaves only 3 conditions ---- R4, R6, and R7 (resembles “exclusive OR” ?! ) √ √ √
Decision Table for Next-Date with Actions Condition 1 Condition 2 Condition 3 Month input T T T T F F F F T T F F T T F F T F T F T F T F Remember : Condition 1: 1 < = m <= 12 Condition 2: m < 1 Condition 3: m > 12 R1 R2 R3 R4 R5 R6 R7 R8 √ √ √ Action 1 Action 2 - - - X - X X - - - X X - - - - Note that R3 has an action defined in the Decision Table. This should trigger a question because the condition can not happen. There should be no action defined for R3 ---- perhaps, a Specification error ? Assume actions defined in the requirements doc.
Advantages/Disadvantages of Decision Table
Allow us to start with a “complete” view, with no consideration of dependence
Allow us to look at and consider “dependence,” “impossible,” and “not relevant” situations and eliminate some test cases.
Allow us to detect potential error in our Specifications
Need to decide (or know) what conditions are relevant for testing - - - this may require Domain knowledge
e.g. need to know leap year for “next date” problem in the book
Scaling up can be massive: 2 n rules for n conditions - - - that’s if the conditions are binary