Increase coverage of custom C code integration in S function

I have a C code program that i have integrated in a S function block in a simulink environment. After analyzing the coverage of the S function block, the decision coverage = 50% and statement coverage = 79%.

I want to increase the coverage of the C program code. Do i need to create test condition in the source code itself or will i be able to get test cases using the Simulink test and Simulink design verifier ?

Note: The C program do not take any sort of inputs.

Thank you in advance.

[Pat Canny]

Hi Rohit - just confirming: are you using R2019b?

[Rohit Roy]

yes i am

Answer 1

[Antoine Requet]

Hello Rohit,

Simulink Design Verifier should be able to generate test cases for S-functions. Depending on how your S-function is compiled, you may have to recompile it to enable support for Design Verifier:

• If you have compiled your S-function with the legacy_code tool, you should set the supportCoverageAndDesignVerifier option to true
• If your S-function is defined in an S-function builder block, you should check the box "Enable Support for Design Verifier" in the "Build Info" tab
• If your S-function is compiled with mex or slcovmex, you should compile it with slcovmex with the -sldv option.

However, I am seeing that you mentioned that the C program does not take any sort of inputs. If that means that your S-function does not have inputs, then it may not be possible to generate additional tests for extending the coverage, since the tests are based on the inputs of the model.

[Rohit Roy]

Thank you Antoine. I am not quite sure what you meant . is it "may not be" or " is not possible" ?

[Antoine Requet]

Hello Rohit,

If your S-function does not have inputs or parameters at all, then Simulink Design Verifier cannot generate additional test cases for extending the coverage of the S-function as-is: the test cases are defined by input values, so no test case can be provided without inputs.

However, depending on your S-function and your objectives, it may still be possible to use design verifier to extend the coverage (but it would require a bit more work) :

• In the case where your S-function does not have inputs, but is accepting parameters, you may be able to use the Design Verifier parameter configuration to extend the coverage by varying the parameters.

• If the coverage is missing because of "hidden" inputs that are not exposed to Simulink, you could modify your S-function to expose them as input or parameter so that they are visible to Simulink. That way, test cases could be generated.