Testing Events In VI Tester
The APIs that you have to test are not always simple. As well as passing data they may involve events (with the front panel or with user events).
The other day I needed to test that an event fired as part of a test case. I could see a generic solution, so I created a template for it. I had two requirements:
- If the event doesn’t fire – test fails.
- If the event fires with the wrong data – test fails.
In my given when then sequence then we end up with a test that follows the structure:
- Given: Who knows, in this case, a UI library has been tied to a control.
- When: We take some action that should cause an event on that control.
- Then: Check the event.
To check the event we create an event structure outside of a loop as we don’t want to handle multiple events. We need two cases:
- A timeout case with a suitable timeout – In this case, we call the Test Case.lvclass:fail.vi to fail the test. This should never run if the when code fired the event.
- A case that handles the event – If you don’t care about the data then you can do nothing here, otherwise, include tests on the data included in the event.
- Dynamic Event Registration: If this is a user event then you will need to register for the event. I’ve included this in my template, but you must move the event registration to the given case. If you haven’t registered the event before the action in the when case, it won’t ever fire.
- Parallel/Dynamic Event Generation: If your event is in some dynamic code you may need to have this running. My advice: DONT. Try and pull out the internal API and test synchronously. Asynchronous testing in LabVIEW introduces timing concerns which make your tests much more complicated.
Where To Get It
If you want to use this template, or even if you are just using VI tester you can download the new version of the VI Tester Advanced Comparisons (VITAC) tool from https://github.com/WiresmithTech/VITAC/releases/tag/v1.1.0.