@Test
  public void fromJsonWithWhiteSpaceStringThrowsIllegalArgumentException() {
    // given: white space string
    String whiteSpaceString = "      ";

    // when: passed to fromJson
    Throwable thrown = catchThrowable(() -> fromJson(whiteSpaceString));

    // then: throws IllegalArgumentException with cause of GfJsonException
    assertThat(thrown).isInstanceOf(IllegalArgumentException.class)
        .hasCauseInstanceOf(NullPointerException.class);
    assertThat(thrown.getCause()).isInstanceOf(NullPointerException.class).hasNoCause();
  }
Unit tests for {@link LocatorLauncher.LocatorState}.
geode-core/src/test/java/org/apache/geode/distributed/LocatorStateTest.java