Bug 444213: add unit test to ensure IClientNotificationService is called

https://bugs.eclipse.org/bugs/show_bug.cgi?id=444213

Change-Id: I6e810dec5e2c8da2bd8a6fa7f80580d0b06dc931
Reviewed-on: https://git.eclipse.org/r/38646
Tested-by: Hudson CI
Reviewed-by: Jeremie Bresson <jbr@bsiag.com>