In Specman, determinant is not constrained by its when subtype attributes

Question

Next question to post:

Hi,

I have the following test case:

<’
 struct item_s {
            payload:list of byte;
            kind:[SMALL,BIG];

            when SMALL item_s {
                            keep payload.size() < 10;
            };
      };

extend sys {
            !item:item_s;

            run() is also {
                       for i from 1 to 10 {
                                gen item keeping {
                                       .payload.size() == 100;
                                       };                             
                             };
                    };
           };
 ‘>

I expected the test to generate only BIG items. Instead, I see that occasionally a SMALL item is generated, which leads to a contradiction. What is the explanation for this behavior?

score 3 · Answer 1 · edited Jun 20 '20 at 09:12

The user guide states that

Any field that is declared or constrained under a when subtype depends on the value of the when determinant. In other words, there is an implicit unidirectional constraint (a subtype dependency) between the when determinant and the dependent field:

when-determinant -> dependent-field

This means that kind and payload are generated separately. You'll need to move your constraint outside of the when subtype:

keep kind == SMALL => payload.size() < 10;

You can find more info in the Working with When Subtype Dependencies in Constraints chapter of the Specman Generation User Guide.

In Specman, determinant is not constrained by its when subtype attributes

1 Answers1