@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_key_is_null() {
    MapSettings underTest = new MapSettings();

    expectKeyNullNPE(() -> underTest.set(null, randomAlphanumeric(3)));
  }