Technique
Consider a system which has 3 parameters and each of them has 3 values. To test all the possible combinations of these parameters (i.e. exhaustive testing) we will need a set of 3^3 = 27 test cases. But instead of testing the system for each combination of parameters, we can use an orthogonal array to select only a subset of these combinations. With orthogonal array technique we can maximize the test coverage while minimizing the number of test cases to consider. We here assume that the pair that the test that maximizes interaction between the parameters, will have more defects and the technique works.
| Test case ↓ | Parameter 1 | Parameter 2 | Parameter 3 |
|---|---|---|---|
| 1 | 1 | 1 | 3 |
| 2 | 1 | 2 | 2 |
| 3 | 1 | 3 | 1 |
| 4 | 2 | 1 | 2 |
| 5 | 2 | 2 | 1 |
| 6 | 2 | 3 | 3 |
| 7 | 3 | 1 | 1 |
| 8 | 3 | 2 | 3 |
| 9 | 3 | 3 | 2 |
Given that assumption, the table shows the set of nine combination of parameters which are sufficient to catch the fault considering the interaction of the input parameters, which is very effective and economical. The array is orthogonal because all possible pair-wise combinations between parameters occurs only once.
The given L9 Orthogonal Array assess result of test cases as follows,
Single Mode Faults - Single mode faults occur only due to one parameter. For example, in above Orthogonal array if test cases 7, 8 and 9 show error, we can expect that value 3 of parameter 1 is causing the error.Likewise we can detect as well as isolate the error.
Double Mode Fault - Double mode fault is caused by the two specific parameters values interacting together. Such an interaction is a harmful interaction between interacting parameters.
Multimode Faults - More than two interacting components if produce the consistent erroneous output, then it is a multimode fault. Orthogonal array detects the multimode faults.
Refer the following link for more details: http://www.51testing.com/ddimg/uploadsoft/20090113/OATSEN.pdf
Read more about this topic: Orthogonal Array Testing
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