@Test
  public void nullDirectory_throwsIllegalArgumentException() throws Exception {
    // arrange
    directory = null;

    // act/assert
    assertThatThrownBy(
        () -> new ControlFileWatchdog(directory, requestFileName, requestHandler, stopAfterRequest))
            .isInstanceOf(NullPointerException.class);
  }
Functional integration tests for {@link ControlFileWatchdog}.
geode-core/src/integrationTest/java/org/apache/geode/internal/process/ControlFileWatchdogIntegrationTest.java