@Test
    public void testFilterValidEmpty() throws Exception
    {
        // Setup fixture.
        final Collection<X509Certificate> input = new ArrayList<>();

        // Execute system under test.
        final Collection<X509Certificate> result = CertificateUtils.filterValid( input );

        // Verify results.
        assertTrue( result.isEmpty() );
    }
Test for {@link CertificateUtils#filterValid(Collection)}. Verifies that an input argument that
is an empty (not-null) collection returns an empty collection.
xmppserver/src/test/java/org/jivesoftware/openfire/keystore/CertificateUtilsTest.java