public static Optional<String> getSystemProperty(String propertyName) {
    return Optional.ofNullable(getSystemProperty(propertyName, null));
  }
@Test
  public void getSystemProperty_whenPropertyNotExistsWithDefaultValue_returnsDefaultValue() {
    assertThat(TsunamiConfig.getSystemProperty(TEST_PROPERTY, "Default")).isEqualTo("Default");
  }