Set<Integer> changedLines() {
    return tracker.changedLines();
  }
@Test
  public void count_single_added_line() throws IOException {
    String example = "diff --git a/file-b1.xoo b/file-b1.xoo\n"
      + "index 0000000..c2a9048\n"
      + "--- a/foo\n"
      + "+++ b/bar\n"
      + "@@ -0,0 +1 @@\n"
      + "+added line\n";

    printDiff(example);
    assertThat(underTest.changedLines()).containsExactly(1);
  }