@Test
public void testGetExtensionOnFilename() {

  final Object[][] testParameters = new Object[][] {{"HelloWorld.png", "png"},
      {"Hello.World.jpg", "jpg"}, {"Hello_World.gif", "gif"}};
  assertNull(FilenameUtils.getExtension(null));
  for (final Object[] testParameter : testParameters) {
    String expected = (String) testParameter[1];
    String filename = (String) testParameter[0];
    assertEquals(expected, FilenameUtils.getExtension(filename));
  }
}