@Test
public void listDirSuffixFiles() {

    assertNull(FileUtil.listDirSuffixFiles((String) null, null));
    assertNull(FileUtil.listDirSuffixFiles((File) null, null));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "notexist", null));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "xxx/yyy/zzz", null));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "log4j.properties", null));
    assertNull(FileUtil.listDirSuffixFiles((String) null, ".properties"));
    assertNull(FileUtil.listDirSuffixFiles((File) null, ".properties"));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "notexist", ".properties"));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "xxx/yyy/zzz", ".properties"));
    assertNull(FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath() + "log4j.properties", ".properties"));
    assertArrayEquals(new File[] {}, FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath(), ".nothissuffix"));
    int expected = new File(ClassLoaderUtil.getClasspath()).listFiles(new FileFilter() {
        public boolean accept(File file) {
            return (file.getName().endsWith(".properties"));
        }
    }).length;
    assertEquals(expected, FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath(), ".properties").length);
    expected = new File(ClassLoaderUtil.getClasspath()).listFiles().length;
    assertEquals(expected, FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath(), null).length);
    assertEquals(expected, FileUtil.listDirSuffixFiles(ClassLoaderUtil.getClasspath(), "").length);
}