static File applicationFile(File parent, String path) {
        return applicationFile(parent, Path.fromString(path));
    }
@Test
    public void testApplicationFile() {
        applicationFile(new File("foo"), "");
        applicationFile(new File("foo"), "bar");
        applicationFile(new File(new File(""), ""), "");
        assertEquals("/ is not a child of ",
                     assertThrows(IllegalArgumentException.class,
                                  () -> applicationFile(new File(""), ""))
                             .getMessage());
        assertEquals("'..' is not allowed in path",
                     assertThrows(IllegalArgumentException.class,
                                  () -> applicationFile(new File("foo"), ".."))
                             .getMessage());
    }