Problem:    When 'matchpairs' is empty every character beeps. (Marco Hinz)
Solution:   Bail out when no character in 'matchpairs' was found.
            (closes #8053)  Add assert_nobeep().

Problem:    Code coverage could be improved.
Solution:   Add a few more tests. (Dominique Pellé, closes #7957)

Problem:    Auto format doesn't work when deleting text.
Solution:   Make "x" trigger auto format. (closes #7504)

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

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

Problem:    Insert mode completion not fully tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #6041)

Problem:    Formatoptions not sufficiently tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #6031)

Problem:    Search code not sufficiently tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5999)

Problem:    various code is not properly tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5871)

Problem:    Channel and sandbox code not sufficiently tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5855)