@Override
  public void add(Component file, Duplication duplication) {
    checkFileComponentArgument(file);
    checkNotNull(duplication, "duplication can not be null");

    duplications.put(file.getKey(), duplication);
  }
@Test
  public void addDuplication_inner_throws_NPE_if_duplication_argument_is_null() {
    assertThatThrownBy(() -> underTest.add(FILE_COMPONENT_1, null))
      .isInstanceOf(NullPointerException.class)
      .hasMessage("duplication can not be null");
  }