CustomTester is a transformer designed for a particular use - where an attribute is set to a value of "unset" it will be changed to a simple null value. The main component is a Grepper in preference to a Tester because the Grepper permits tests regardless of case, so it would find "unset", "UNSET" or "uNsEt".

It isn't a particularly complicated transformer, but it is a good example of sharing a published parameter.

Here's the custom transformer definition...


...and here's a workspace using it...