How does pairwise parameterization work in the unit test framework?

I have studied the example script in the documentation, but I can't see how the test parameters are being chosen in "pairwise" fashion. Why is the number of combinations 10 in this example? What is the algorithm to generate pairwise parameters?

[Siriniharika Katukam]

Can you provide the link of the example you have referred to?

[Brett Pantalone]

https://www.mathworks.com/help/matlab/matlab_prog/create-advanced-parameterized-test.html#d117e84603

[Greg]

8 months later and nothing on this? The documentation is extremely minimal on this, which is surprising and disappointing considering how thorough MATLAB documentation typically is. I would ask the additional question of what "pairwise" even means given the example has 3 input parameters - a group of 3 is not called a pair.

Answer 1

[Greg]

According to an answer on stack exchange, the minimum number of pairwise combinations is 9. The concept of pairwise combination takes any 2 parameters at a time, and doesn't care about the rest. The trivial solution to the example is:

1. dim1.small x dim2.small x dim3.small
2. dim1.small x dim2.medium x dim3.medium
3. dim1.small x dim2.large x dim3.large
4. dim1.medium x dim2.small x dim3.medium
5. dim1.medium x dim2.medium x dim3.large
6. dim1.medium x dim2.large x dim3.small
7. dim1.large x dim2.small x dim3.large
8. dim1.large x dim2.medium x dim3.small
9. dim1.large x dim2.large x dim3.medium

We have every possible value pair you could draw from any pair of parameters, but we do not have every unique triplet (that would be the "exhaustive" approach, and result in 3x3x3 = 27 combinations).

I still have no idea where 10 comes from in the documentation example.

Answer 2

[Alex Kashuba]

I think the answer is following. Let say we have parameters

classdef PairwiseTest < matlab.unittest.TestCase
    properties (TestParameter)
        a = { '1', '2', '3', '4', '5'}
        b = { '1', '2', '3', '4', '5'}
        c = { '6', '7', '8'}
        d = { '0', '9'}
    end  
    methods(Test, ParameterCombination='pairwise')
        function testPairwise(tc, a, b, c, d)
            fprintf(['\n' a b c d ])
        end
    end
    methods(Test, ParameterCombination='exhaustive')
        function testPairAC(tc, a, c)
            fprintf(['\n' a '_' c '_' ])
        end
    end
end

We get here for testPairwise

1160.
1279.
1380.
1469.
1560.
2170.
2260.
2369.
2480.
2579. 
3189.
3260.
3379.
3470.
3589.
4160.
4289.
4370.
4479.
4580. 
5160.
5279.
5389.
5460.
5579.

The run gives us such combinations that any pair of parameters (say a and c, but can be any other) are exhaustive i.e. all combitations of testPairAC are included:

1_6_.
1_7_.
1_8_.
2_6_.
2_7_.
2_8_.
3_6_.
3_7_.
3_8_.
4_6_. 
4_7_.
4_8_.
5_6_.
5_7_.
5_8_.

[Ashley Trowell]

Well this is a very direct way to get to the answer.

Answer 3

[Houman Rastegarfar]

The documentation now provides more information about pairwise parameter combination. For details, see https://www.mathworks.com/help/matlab/matlab_prog/use-parameters-in-class-based-tests.html#mw_292dd6d4-5538-4bcc-9ab8-70cd798333bd