The new oldtest directory is in test/old/testdir. The reason for this is
that many tests have hardcoded the parent directory name to be
'testdir'.

Problem:    Memory allocation failures for new tab page not tested.
Solution:   Add tests with failing memory allocation. (Yegappan Lakshmanan,
            closes vim/vim#10067)

https://github.com/vim/vim/commit/72bb47e38f6805050ed6d969f17591bed71f83d4

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    Buffer allocation failures insufficiently tested.
Solution:   Add tests for memory allocation failures. (Yegappan Lakshmanan,
            closes vim/vim#10064)

https://github.com/vim/vim/commit/0dac1ab5791819ee9a496273eea38f69a217ac45

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    Using NULL regexp program.
Solution:   Check for regexp program becoming NULL in more places.

https://github.com/vim/vim/commit/b62dc5e7825bc195efe3041d5b3a9f1528359e1c

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    There is no good test for CursorHold.
Solution:   Add a test.  Remove duplicated test. (Yegappan Lakshmanan,
            closes vim/vim#6503

https://github.com/vim/vim/commit/7591116acffc45b5880c49244646651badac1629

Problem:    Not enough tests for writing buffers.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes vim/vim#8229)

https://github.com/vim/vim/commit/46aa6f93acb5d932d2893606d980a6b4b8a9594c

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    MS-Windows: test sometimes runs into existing swap file.
Solution:   Use a different file name.

https://github.com/vim/vim/commit/f8bc0ce2671d7f7f73760f665b52e4f00a1bbcac

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Failure to compile a pattern not tested much.
Solution:   Add tests where a pattern fails to compile. (Yegappan Lakshmanan,
            closes vim/vim#7004)

https://github.com/vim/vim/commit/531be47ac5522807b265c6287021a01c9b895ac9

Problem:    assert_fails() checks the last error message.
Solution:   Check the first error, it is more relevant.  Fix all the tests
            that rely on the old behavior.

https://github.com/vim/vim/commit/9b7bf9e98f06ece595fed7a3ff53ecce89797a53

Skip test_listener.vim, test_textprop.vim, test_viminfo.vim.
Skip test_python2.vim: affected line fails and hasn't been ported.
Skip test_python3.vim: affected lines fail and haven't been ported.
Skip CHECK_LIST_MATERIALIZE.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Insufficient tests for src/buffer.c.
Solution:   Add more tests.  Move comments related tests to a separate file.
            (Yegappan Lakshmanan, closes vim/vim#6325)
https://github.com/vim/vim/commit/b7e2483655d9b68df0c7349918027d800051a28a