Problem:    Various code lines not covered by tests.
Solution:   Add test cases. (Dominique Pellé, closes #8178)

Problem:    Using "syn include" does not work properly.
Solution:   Don't add current_syn_inc_tag to topgrp. (Jaehwang Jerry Jung,
            closes #8104)

Problem:    Transparent syntax item uses start/end of containing region.
Solution:   Do not change the startpos and endpos of a transparent region to
            that of its containing region. (Adrian Ghizaru, closes #7349,
            closes #7391)

Problem:    "syn sync" reports a very large number.
Solution:   Use "at the first line".

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

Problem:    Crash when using ":set" after ":ownsyntax".
Solution:   Make sure 'spelloptions' is not NULL. (closes #6950)

Problem:    Tests do not check the error number properly.0
Solution:   Add a colon after the error number. (closes #6869)

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:    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.

Problem:    Search() cannot skip over matches like searchpair() can.
Solution:   Add an optional "skip" argument. (Christian Brabandt, closes #861)