@Override
  public String create() {
    int currentId = id.getAndIncrement();
    return UUID_PREFIX + StringUtils.leftPad(String.valueOf(currentId), 12, "0");
  }
@Test
  public void generate_sequence_of_integer_ids() {
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000001");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000002");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000003");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000004");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000005");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000006");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000007");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000008");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000009");
    assertThat(underTest.create()).isEqualTo("00000000-0000-0000-0000-000000000010");
  }