public static Optional<String> getSystemProperty(String propertyName) {
    return Optional.ofNullable(getSystemProperty(propertyName, null));
  }
@Test
  public void getSystemProperty_whenPropertyExists_returnsPropertyValue() {
    System.setProperty(TEST_PROPERTY, "Test value");

    assertThat(TsunamiConfig.getSystemProperty(TEST_PROPERTY)).hasValue("Test value");
  }