public Protocol forNameOrDefault(final String identifier) {
        return forNameOrDefault(identifier, null);
    }
@Test
    public void testForNameOrDefaultMissing() throws Exception {
        final TestProtocol dav = new TestProtocol(Scheme.dav);
        final ProtocolFactory f = new ProtocolFactory(Collections.singleton(dav));
        assertEquals(dav, f.forNameOrDefault("dav"));
        assertNull(f.forNameOrDefault("ftp"));
    }