> cat test/hotspot/jtreg/BadModules.java
/*
 * @test
 * @modules jdk.base/jdk.internal.loader
 * @run main BadModules
 */
public class BadModules {
    public static void main(String[] args) {
        jdk.internal.loader.ClassLoaders.class.toString();
    }
}

The above test specifies a non-existent module (jdk.base) in a @modules tag. However, when running this test with jtreg, only a "no tests selected" message is shown:

> jtreg test/hotspot/jtreg/BadModules.java
Test results: no tests selected
Report written to /Users/dnsimon/dev/jdk-jdk/open/JTreport/html/report.html
Results written to /Users/dnsimon/dev/jdk-jdk/open/JTwork

It would be clearer if jtreg says something about the invalid @modules tag (which I assume it has detected).