lowerdir, upperdir and the expected overlay are in the tarballs
the description of the test cases are listed below:

file name                   lowerdir upperdir
                            (D: directory, F: file, SL: symlink, W: whiteout)
                            (number for permission bits, * for modified content)

removed_tests               D, 755   D, 755
  removed_dir               D, 755   W
    subdir                  D, 755
      a.txt                 F, 755
    b.txt                   F, 755
  empty_removed_dir         D, 755   W
  replaced by a file        D, 755   F, 600
    a.txt                   F, 644
    this_was_a_subdir       D, 755
      c.txt                 F, 400
  replaced_by_symlink       D, 700  SL, -
    another_subdir          D, 700
  replaced_by_opaque        D, 700  DO, 755
    origin\subdir           D, 755
      dir                   D, 755
        file                F, 644
      a_file                F, 755
    new_subdir                       D, 755
    new_file                        SL, 400
normal_merged_dir           D, 755   D, 755
    a_file                  F, 644   F, 644
    only_old                F, 644   W
    only_new                        SL, -
    changed" "file          F, 644   F, 644*
    changed_symlink        SL, -    SL, -  *
    unchanged'symlink      SL, -
    trivial_dir             D, 755   D, 755
      a_file                F, 644   F, 644
      a\link               SL, -    SL, -
    more_test               D, 755   D, 755
      by_opaque             D, 755  DO, 755
        a_file              F, 644
        another_file        F, 644
        third_file          F, 755
      file_to_link          F, 644  SL, -
      link_to_file         SL, -     F, 755
modified_dir                D, 755   D, 755
  sub_1                     D, 755   D, 755
    permission              D, 755   D, 700
      changed$file          F, 755   F, 755*
      dir                   D, 700   D, 755
    sub_2                   D, 777   D, 777
      added_file                     F, 400
      sub_3                 D, 700   D, 700
        file                F, 644   F, 644*
        sub_4               D, 755   D, 755
          removed           D, 700   W
          added                      D, 700
  created                            D, 755
    sub_1                            D, 755
      sub"2                          D, 755
permission                  D, 755   D, 755
  file                      F, 400   F, 600
  changed_file              F, 400   F, 644*
  path_1                    D, 700   D, 500
    another_path            D, 700
  path_2                    D, 755   D, 700
    another path            D, 700   D, 755
      a_file                F, 400   F, 400
deleted_files               D, 755   D, 755
  file_by_dir               F, 644   D, 755
  link-by-dir              SL, -     D, 755
    sub_dir                          D, 755
  dir_whiteout              D, 755   W
