@Test
public void getIdentifierURL() throws Exception {

	assertEquals(-1, this.xml.getIdentifier(new URL("file:x"))); //$NON-NLS-1$
	assertEquals(2, this.xml.getIdentifier(new URL("file:a.txt"))); //$NON-NLS-1$
	assertEquals(3, this.xml.getIdentifier(new URL("file:b.txt"))); //$NON-NLS-1$
	assertEquals(4, this.xml.getIdentifier(new URL("file:a.jpg"))); //$NON-NLS-1$
}