public Map<String, String> getCharacteristics() {
    return characteristics;
  }
@Test
  public void setCharacteristics_null_is_considered_as_empty() {
    CeTask task = underTest.setType("TYPE_1").setUuid("UUID_1")
      .setCharacteristics(null)
      .build();
    assertThat(task.getCharacteristics()).isEmpty();
  }