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:    Check commands don't work well with Vim9 script.
Solution:   Improve constant expression handling.

https://github.com/vim/vim/commit/7f829cab356d63b8e59559285593777a66bcc02b

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

Problem:    Exit test causes spurious valgrind reports.
Solution:   Skip test.  Add CheckNotValgrind.

https://github.com/vim/vim/commit/cf801d4b95180ddaee1bf633ef482232625dd80b

Cherry-pick RunningWithValgrind() from patch 8.2.5136.

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

Problem:    Tests have clumsy check for X11 based GUI.
Solution:   Add CheckX11BasedGui.

https://github.com/vim/vim/commit/40bd5a15405206b130d487af0ca61b5d9b5859f8

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

Problem:    Check for $DISPLAY never fails.
Solution:   Use eval().

https://github.com/vim/vim/commit/f6d877975ba93fc9b4bee2c5d2aff88dbf9bea59

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

Problem:    Test for remote_foreground() fails. (Elimar Riesebieter)
Solution:   Check that $DISPLAY is set. (Christian Brabandt)

https://github.com/vim/vim/commit/d6fa7bd5b900dd363d3a824e0ebe3619a1634df6

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

Problem:    Recover test fails on FreeBSD.
Solution:   Check for Linux.

https://github.com/vim/vim/commit/6635ae1437e6e343c0514524a8dfb19d9525b908

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

Problem:    No need to check for BSD after checking for not root.
Solution:   Remove CheckNotBSD. (Ozaki Kiichi, closes vim/vim#7989)

https://github.com/vim/vim/commit/4355894869355c185e7810e67d52802453576e81

Problem:    Various functions not properly tested.
Solution:   Add more tests, especially for failures. (Yegappan Lakshmanan,
            closes vim/vim#5843)

https://github.com/vim/vim/commit/0e05de46226eb4e5ea580beefa71831f92d613d3

Cherry-pick test changes from patch 8.2.0427 and skip Test_has().
Cherry-pick Test_complete_wildmenu() change from patch 8.2.4339.

Problem:    Tests use hand coded feature and option checks.
Solution:   Use the commands from check.vim in more tests.

https://github.com/vim/vim/commit/8c5a278fc508da6dfe50e69b6ee734451aa4eafb

Omit Test_wincolor(): there are later patches that touch that function.
Omit test_memory_usage.vim: a Lua test is used for that file.
Cherry-pick Test_issue_3969() from patch 8.1.0969.

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