@Test
public void testtoRelativePath() {

    File base = new File("/data/media/0");
    File file = new File("/data/media/0/Music/somefile.mp3");
    assertThat(toRelativePath(base, file)).isEqualTo("Music/somefile.mp3");
    //make sure it reassembles to the same file
    assertThat(file).isEqualTo(new File(base, toRelativePath(base, file)));
}