@Test
  public void fromJsonWithNullStringThrowsNullPointerException() {
    // given: null string
    String nullString = null;

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

    // then: throws IllegalArgumentException
    assertThat(thrown).isInstanceOf(IllegalArgumentException.class)
        .hasCauseInstanceOf(IllegalArgumentException.class);
    assertThat(thrown.getCause()).isInstanceOf(IllegalArgumentException.class).hasNoCause();

  }
Unit tests for {@link ServerLauncher.ServerState}.
geode-core/src/test/java/org/apache/geode/distributed/ServerStateTest.java