Test coverage could improve

[holdenweb]

Though in fact when I look at the latest testing results it's not as bad as I thought now I've done some refactoring:

Name                              Stmts   Miss  Cover
-----------------------------------------------------
src/textual_forms/__init__.py         1      0   100%
src/textual_forms/app.py             28      7    75%
src/textual_forms/field.py           58     17    71%
src/textual_forms/form.py            74     21    72%
src/textual_forms/validators.py      15      2    87%
src/textual_forms/version.py          1      0   100%
src/textual_forms/widget.py          34      4    88%
-----------------------------------------------------
TOTAL                               211     51    76%
=================================== 10 passed in 3.30s ===...===