### Question:
DirPoll extends SimpleLogSource implements Runnable, FilenameFilter, Configurable, Destroyable { public void setResponseDir (String dir) { responseDir = new File (basePath, dir); } DirPoll(); synchronized void setPath(String base); void setShouldTimestampArchive(boolean shouldTimestampArchive); void setArchiveDateFormat(String dateFormat); void setShouldArchive(boolean shouldArchive); void setShouldCompressArchive(boolean shouldCompressArchive); void setAcceptZeroLength(boolean acceptZeroLength); String getPath(); void setRequestDir(String dir); void setResponseDir(String dir); void setTmpDir(String dir); void setBadDir(String dir); void setRunDir(String dir); void setArchiveDir(String dir); void setPollInterval(long pollInterval); void setResponseSuffix(String suffix); long getPollInterval(); void setProcessor(Object processor); boolean isRegexPriorityMatching(); void setRegexPriorityMatching(boolean regexPriorityMatching); Object getProcessor(); void setConfiguration(Configuration cfg); void setPriorities(String priorities); synchronized void setThreadPool(ThreadPool pool); boolean accept(File dir, String name); void run(); void destroy(); void createDirs(); void addPriority(String fileExtension); void pause(); void unpause(); boolean isPaused();  }### Answer:
@Test public void testSetResponseDirThrowsNullPointerException() throws Throwable { DirPoll dirPoll = new DirPoll(); try { dirPoll.setResponseDir(null); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { assertNull(ex.getMessage(), "ex.getMessage()"); } }