If you have
<path to test project>/build.xml file rename it.
I was able to generate test coverage report by executing following from the console:
<path to android tools>android update test-project -m <path to app project> -p <path to test project> + Enter,
cd <path to test project> + Enter,
ant emma debug install test + Enter,
<path to android tools> is
/opt/android-sdk-linux/tools/ on my machine - the folder where android SDK is installed.
<path to test project>/bin/coverage.html file.
If you get "wrong JAVA_HOME" error execute
gksu gedit /etc/environment + Enter, correct
JAVA_HOME, save the file, log out or reboot and try again.