I develop on Glassfish with a blank admin password.
On http://svn.plexus.codehaus.org/browse/~raw,r=43/cargo-contrib/glassfish/src/main/java/org/codehaus/cargo/container/glassfish/GlassFishStandaloneLocalConfiguration.java I found:
Oh yes, when system property with password is set, then it's validated (ekhm...) against length. When properties come from /tmp/cargo/conf/password.properties - not. This weird validation should be removed.
A workaround for now is to keep the blank password in /tmp/cargo/conf/password.properties...