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jvh75021

String value - No comparison

Status: New

Would like to have the choice of "No Comparison" for a string value test like there is for numeric value test.

 

jvh

8 Comments
Jervin Justin
NI Employee (retired)

Hi jvh,

 

Can you please explain your use case to us so that we can better evaluate this idea?

 

Thanks,

Jervin Justin

Jervin Justin
NI TestStand Product Manager
Josh_W
Active Participant

Jervin, I have a customer with this same use case.

 

In the setup that they are using, they have strings coming back from an instrument.  In most cases, those strings are pre-defined characters (like the instrument identification, ACK, etc.) that they can directly compare to make sure they got the right response.  So their instrument query function is wrapped into a custom step type that is merged with the String Value Test step type.

 

However, in some cases the number of characters is not known ahead of time, and depends on where in the TPS the function is called. In this case, the customer wanted the ability to call their usual instrument custom step type, but to have a 'no comparison' case. That way they could use a subsequent step to evaluate the instrument's response.

Josh W.
Certified TestStand Architect
Formerly blue
Jervin Justin
NI Employee (retired)

Let me make sure I understand...

While this use case could be accomplished by performing the 'dummy' test step (that gets the unknown response) as an action step (instead of a string limit test), they'd rather not have to create another custom step to do this.

 

Is that accurate?

Jervin Justin
NI TestStand Product Manager
Josh_W
Active Participant

Yes. That is accurate.

 

This custom step type library is for re-use across an organization of 10-20 people, and it is going to be used by developers without any training on the step types, and who probably don't know TestStand that well.  So adding a very similar step that has only slightly different behavior is considered undesirable because of training and maintenance concerns

Josh W.
Certified TestStand Architect
Formerly blue
andreas.he
Member

For tracabillity, logging MAC addresses from ethernet- wireless- and bluetooth- adapters or storing the serial number of power supply modules are becoming more important and require such a solution. Meaning more fexible (or no) comparsion on string based values.

 

OgZilla
Member

As a workaround for those who need this functionality now; you can set the 'Expected String Value:' on the Limits tab to 'Step.Result.String' (or whatever your 'Data Source Expression:' is defined as. This ensures that the test will never fail by comparing the string value to itself and the data will be collected as desired.

andreas.he
Member

Hi

Thanks for the hint, that's the well known workaround, which everybody uses.

But then it looks, as if this test step had been executed with different limits. Validated test systems used in medical or defense environment has to be validated, meaning the limits have to be certified and released by the customers quality regulations.

Many measuring data collecting/processing system check, if limits were changed within  production lots, which is not allowed. So you have two choices, to explain the customer that his requirements do not make sense or that we can not meet his requirements with NI software framework. 

 

Andreas

 

 

crossrulz
Knight of NI

I think I accomplished this goal by using an Additional Result to log the string value.  Need to double-check when I get into the office next week.


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