The file JSR166TestCase has two @test blocks. Both are found when jtreg is invoked with an arg of the directory containing the file, but not when passed just the file directly.

Mysterious failure to run tests seems pretty serious.

 $ for arg in '' JSR166TestCase.java; do echo ---; jtreg -testjdk:/home/martin/ws/jdk9/build/linux-x86_64-normal-server-release/images/jdk -noreport -agentvm -verbose:all java/util/concurrent/tck/$arg |& grep ACTION: ; done
---
ACTION: build -- Passed. All files up to date
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful
ACTION: build -- Passed. All files up to date
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful
---
ACTION: build -- Passed. All files up to date
ACTION: build -- Passed. All files up to date
ACTION: junit -- Passed. Execution successful