@Test
public void returnsNullReaderKeyIfReaderKeyEqualsWriterKey() {

    // given
    KeySequenceConfig config = createDefaultTestKeySequenceConfig();
    KeySequence sequence = createDefaultTestUUIDSequence(config);
    // when
    CharSequence readerKey1 = sequence.nextReaderKey();
    CharSequence readerKey2 = sequence.nextReaderKey();
    // then
    assertNull(readerKey1);
    assertNull(readerKey2);
}