After a collegue of mine updated the Java version to 1.7 on our JMeter Jenkins slave (running on CentOS) all JMeter Projects stopped running.
The error message was:
Uncaught Exception java.lang.UnsatisfiedLinkError: /usr/java/jdk1.7.0_45/jre/lib/amd64/xawt/libmawt.so: libXtst.so.6: cannot open shared object file: No such file or directory.
When executed on console it worked.
I fired up a Vagrant VM and added this as Jenkins slave. JMeter worked on this slave also.
So I thought there must be something wrong with the Java installation.
When I searched for the missing library I found the solution:
[--@--]# locate libXtst.so.6
/usr/java/jdk1.6.0_29/jre/lib/amd64/xawt/libXtst.so.6
/usr/lib/libXtst.so.6
/usr/lib/libXtst.so.6.1.0
[--@--]# ll
/usr/java/jdk1.6.0_29/jre/lib/amd64/xawt/libXtst.so.6
lrwxrwxrwx 1 root root 10 Jul 16 2012
/usr/java/jdk1.6.0_29/jre/lib/amd64/xawt/libXtst.so.6 -> libmawt.so
The solution was to create a symbolic link:
[--@--]# cd /usr/java/jdk1.7.0_45/jre/lib/amd64/xawt/
[--@--]# ln -s libmawt.so libXtst.so.6
Clifford Sanders 
Had same error trying to run Portecle on Java 1.7.0_45 on CentOS 6.5 – the symlink solved the problem. THANKS! for posting this.