@Test
public void testListAllFiles_withFileExtension() throws Exception {

	File dir = this.folder.newFolder();
	Assert.assertTrue( new File( dir, "f1.txt" ).createNewFile());
	Assert.assertTrue( new File( dir, "f2.jpg" ).createNewFile());
	Assert.assertTrue( new File( dir, "f3.txt" ).createNewFile());
	Assert.assertTrue( new File( dir, "f4.JPG" ).createNewFile());
	Assert.assertTrue( new File( dir, "f5.zip" ).createNewFile());
	Assert.assertEquals( 2, Utils.listAllFiles( dir, "jpg" ).size());
	Assert.assertEquals( 2, Utils.listAllFiles( dir, ".jpg" ).size());
	Assert.assertEquals( 2, Utils.listAllFiles( dir, "jPg" ).size());
	Assert.assertEquals( 2, Utils.listAllFiles( dir, "txt" ).size());
	Assert.assertEquals( 1, Utils.listAllFiles( dir, ".zip" ).size());
	Assert.assertEquals( 5, Utils.listAllFiles( dir, null ).size());
}