getting eclipse-TestNG to work on Fedora 23

On Fedora 23 with Eclipse and TestNG I am getting an error
whenever I try to run a TestNG class.  The entire system was
updated (using yum (DNF) extender) within the last 24 hours;
versions of (what I think are) relevant packages are:
eclipse-filesystem 1.0-5.fc23, eclipse-jdt 4.5.2-10.fc23,
eclipse-platform 4.5.2-10.fc23, eclipse-testng 6.8.6-6.fc23,
testng 6.8.21-2.fc23

Minimal test case (to reproduce):
Starting with a completely new workspace:
File > New > Project > Java Project
enter name "Trivial"
Finish
Click Yes in the "Open Associated Perspective?" dialog
File > New > Package
enter name "com.testng.minimalDemo"
Finish
Right-click "com.testng.minimalDemo" under Trivial/src in Package Explorer
Select TestNG > Create TestNG class
Select all entries in Annotations
Finish

This created NewTest.java, which had multiple errors flagged;
the first was "The import org.testng cannot be resolved"

Applying the first Quick Fix "Add TestNG library" cleared all of
those errors, but then

Run > Run As > TestNG Test

paused for a few seconds and displayed an error box:

Couldn't launch TestNG
    Couldn't contact the RemoteTestNG client. Make sure you don't have an older
    version of testng.jar on your class path.

Reason:
    Timeout while trying to contact RemoteTestNG

I don't have an older version of testng.jar anywhere --
only the one installed by eclipse-testng 6.8.6-6.fc23.

The console shows:

Error: A JNI error has occurred, please check your installation and try again
    Exception in thread "main" java.lang.NoClassDefFoundError: com/beust/jcommander/ParameterException
            at java.lang.Class.getDeclaredMethods0(Native Method)
            at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
            at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
            at java.lang.Class.getMethod0(Class.java:3018)
            at java.lang.Class.getMethod(Class.java:1784)
            at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
            at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
    Caused by: java.lang.ClassNotFoundException: com.beust.jcommander.ParameterException
            at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
            at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
            ... 7 more

So it seems there are (at least) two bugs in TestNG, and/or in its
eclipse plugin, and/or in its Fedora packaging:
1.  Clicking Finish in the Create TestNG class dialog should have
added the TestNG library to the project if not already there.  I should
not have had to add it manually.
2.  Something in the eclipse-testng plugin should have taken care
of whatever additional configuration is needed to avoid that "JNI error".

How do I get past this?