I have seen this behavior in several tests. For instance, test/javax/transaction/testng/Driver.java

If I add "*@modules java.sql java.transaction" to the test description, the test will be silently skipped by jtreg. If I remove "java.transaction", it will run well.
The problem looks related with the line "* @compile -addmods java.transaction". A test will be skipped when there are the same modules declared by @modules or -addmods.

Please confirm if it is legal to have the same module name in @modules or -addmods. If so, I think it is a jtreg bug.
Even it is not illegal to declare duplicate, it looks not a good practice to just skip the test. This may lead to unexpected exclusion of tests. I would suggest to fail with error.