- test additional cases _close_ to these bugs as well
for #1485
- show odd `@Html.CheckBox()`, `@Html.Hidden()` behaviour in unit tests
- show odd `@Html.TextBox()` behaviour in functional tests (templates)
for #1487
- show odd `@Html.Value()` behaviour in unit tests
- show odd `@Html.RadioButton()`, `@Html.TextArea()` behaviour in functional tests
- show lack of validation attributes for `@Html.RadioButton()`, `<select>` tag helper
for #2662
- show odd `@Html.RadioButton(string.Empty)` behaviour in functional tests
for #2664
- show failures with `@Html.ListBox()` in unit tests
nits:
- test `IHtmlHelper` methods, not extensions
- use `ViewData`, not `ViewBag` in `HtmlGeneration_FormController`
- name test methods a bit more consistently
- rename `HtmlHelperValueExtensionsTest` to `HtmlHelperValueTest`
