You've accidentally left out the space between the end of the classpath (...;.) and the beginning of the name of the class to run (junit.swingui.TestRunner), leaving the JVM to decide that what you intended as the argument to the test runner (HelloTest) is the name of the class to run. Then the JVM can't find it, because the classpath doesn't have the "." entry you intended it to have!
So add a space after ";." and before "junit.swingui", and everything should work just fine.