@Test()
    public void testGetNonExistingGroup() throws Exception
    {
        // Setup test fixture.
        HybridGroupProvider.PRIMARY_PROVIDER.setValue(TestGroupProvider.NoGroupProvider.class);
        HybridGroupProvider.SECONDARY_PROVIDER.setValue(TestGroupProvider.LittleEndiansGroupProvider.class);
        HybridGroupProvider.TERTIARY_PROVIDER.setValue(TestGroupProvider.BigEndiansGroupProvider.class);
        final HybridGroupProvider provider = new HybridGroupProvider();

        // Execute system under test & Verify results.
        assertThrows(GroupNotFoundException.class, () -> provider.getGroup("non-existing-group"));
    }
Verifies that an exception is thrown when a non-existing group is being requested.
xmppserver/src/test/java/org/jivesoftware/openfire/group/HybridGroupProviderTest.java