Domain Testing: Divide and Conquer - Testing Education

Appendix E: Guidelines for Filling in “All-Pairs Combination” Table 1
1. Select the variables that you want to combine using all-pairs combination
technique. Only independent variables should be combined using all-pairs
technique. Do not include dependent variables because when such variables are
combined with the remaining variables using all-pairs combination technique will
lead to many impossible combinations due to one or more dependency
relationships amongst the variables. Test dependent variables separately and use
separate combinations that test for specific dependencies.
2. For each independent variable, decide which test cases would be interesting and
useful enough to be included in all-pairs combination. Typically such test cases
are the ones, which when tested individually, the program is expected to give a
reasonably acceptable outcome or in other words the program is expected to
process or handle them correctly. Test cases that were included in the equivalence
class analysis table intentionally to see how the program mishandles them, also
called error handling test cases, are not good choices for all-pairs combination.
This is because including such test cases will render other acceptable pairs in the
corresponding combination(s) in all-pairs table useless. Error handling cases
should be tested separately and if required one might combine error handling test
cases of multiple variables together to see how the program handles multiple
faults at the same time.
3. Sort the independent variables in the descending order of the number of
corresponding representatives or test cases chosen. Get the first two in the sorted
list and assign the number of test case values they have to Max 1 and Max 2
respectively.
4. Give symbolic names to test cases of each variable. For example, represent the
test cases of a variable ‘x’ as X1, X2…Xn
5. No. of rows in your table will be (Max 1 x Max 2), which is the minimal number
of combinations you will have with all-pairs technique. The total no. of rows will
also include blank rows in between which will be in addition to the number of
rows corresponding to combinations of test cases (Max1 x Max2). We might not
be able to fit in all pairs of all variables in this minimal number of combinations,
in which case, additional combinations might have to be added (more on this in
step 12). For now, let us work with Max1 x Max2 being the number of
combinations.
6. No. of columns = total number of variables + 1 (to hold the test case number).
“Test case#” goes in the cell in first row and first column.
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These guidelines were adapted from “Lessons Learned in Software Testing” by Kaner, Bach and
Pettichord.
© Sowmya Padmanabhan, 2003
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