@Override
  protected void set(String key, String value) {
    props.put(
      requireNonNull(key, "key can't be null"),
      requireNonNull(value, "value can't be null").trim());
  }
@Test
  public void set_throws_NPE_if_value_is_null() {
    MapSettings underTest = new MapSettings();

    assertThatThrownBy(() -> underTest.set(randomAlphanumeric(3), null))
      .isInstanceOf(NullPointerException.class)
      .hasMessage("value can't be null");
  }