If you want to run just one test do this:
1. Go to the module where your tests live. In my case it is here:
MBPro-2:ui-common apple$ pwd
/Users/apple/Documents/workspace/svn/TRT-1##9/t0-mvn/ui-common
MBPro-2:ui-common apple$
2. Then run the test
mvn -Dtest=HostlistExprTestGWT test
HostlistExprTestGWT is the name of the test without its extension.