public Optional<String> extract(final String uri) {
        if (uri.startsWith(this.target) && uri.length() != this.target.length()) {
            return Optional.of(uri.replaceFirst(this.target, ""));
        }

        return empty();
    }
@Test
    public void should_return_null_if_uri_does_not_match() {
        MountTo to = new MountTo("/dir");
        assertThat(to.extract("/target/filename").isPresent(), is(false));
    }