@Test
    public void testSingleCollectionWithoutDuplicates() throws Exception
    {
        // Setup test fixture.
        final List<String> input = Arrays.asList("a", "b", "c");

        // Execute system under test.
        @SuppressWarnings("unchecked")
        final Set<String> result = CollectionUtils.findDuplicates(input);

        // Verify results.
        assertTrue(result.isEmpty());
    }
Verifies that {@link CollectionUtils#findDuplicates(Collection[])} does not find duplicates when the provided
singular collection does not have any.
xmppserver/src/test/java/org/jivesoftware/util/CollectionUtilsTest.java