When the HtmlEditor has an error message it should show its error status. This by default means that it should show with a reddish background. The reddish background is usually done by adding the css class ui-input-err to the DOM element.
This page has two HtmlEditor controls, both set to "mandatory". The validate button just calls bindErrors(), so that should cause that red second control.
In addition, when the page is refreshed (F5) that thing should again be red.
The test written for this can be found in ITHtmlEditorComponentTest, and works as follows:
If this works the tests refreshes the page, and then does the same test.