Problem:    On slow systems tests can be flaky.
Solution:   Use TermWait() instead of term-wait(). (Yegappan Lakshmanan,
            closes #6756)

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)

Problem:    Tabpage menu and tabline not sufficiently tested.
Solution:   Add tests. (Yegappan Lakshmanan, closes #6307)

Problem:    Various parts of code not covered by tests.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #6300)

Problem:    Some errors are not covered by tests.
Solution:   Add a few more tests. (Dominique Pelle, closes #5920)

Problem:    :digraph! not tested.
Solution:   Add a test. (Dominique Pelle, closes #5925)

Problem:    Several errors are not tested for.
Solution:   Add tests. (Yegappan Lakshmanan, closes #5892)

Problem:    Various code not covered by tests.
Solution:   Add more test coverage. (Yegappan Lakshmanan, closes #5720)

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)

Problem:    Some balloon tests don't run when they can.
Solution:   Split GUI balloon tests off into a separate file. (Ozaki Kiichi,
            closes #4538)  Change the feature check into a command for
            consistency.