private void assertFileNameEquals(String expected,String initial) {
        assertEquals(expected,ComponentId.fromFileName(initial).toFileName(),"'" + initial + "' became id '" + ComponentId.fromFileName(initial) + "' which should become '" + expected + "'");
    }
Takes two id file names as input
container-core/src/test/java/com/yahoo/component/test/ComponentIdTestCase.java