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

Problem:    Vim9: no error for missing ] after list.
Solution:   Add error message. Add more tests.

Problem:    Code in eval.c not sufficiently covered by tests.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5815)

Problem:    Tests fail when the float feature is disabled.
Solution:   Skip tests that don't work without float support.

Problem:    Crash when evaluating expression with error. (Dhiraj Mishra)
Solution:   Check parsing failed. (closes #5329)

Problem:    Testing lambda with timer is slow.
Solution:   Do not test timer accuracy, only that it works. (Daniel Hahler,
            closes #4723)

Problem:    Code for Blob not sufficiently tested.
Solution:   Add more tests.  Fix uncovered crash.  Add test_null_blob().

Problem:    Test files still use function!.
Solution:   Remove the exclamation mark.  Fix overwriting a function.