I suspect the problem is that you’ve put the “-D” after the -jar. Try this:
java -Dtest="true" -jar myApplication.jar
From the command line help:
java [-options] -jar jarfile [args...]
In other words, the way you’ve got it at the moment will treat -Dtest="true" as one of the arguments to pass to main instead of as a JVM argument.
(You should probably also drop the quotes, but it may well work anyway – it probably depends on your shell.)