[#680] HelpWindowTest: Write header comments concerning possible test failure (#694)
[#680] HelpWindowTest: Write header comments concerning possible test failure (#694)

HelpWindowTest fails on certain computers. The cursor does not move to
the correct location, resulting in the wrong UI component being
clicked. We suspect this to be a bug in the TestFX library.

This causes the wrong UI component to be in focus, which leads to a
test failure.

Let's show an error message when the test fails.
damithc/addressbook-level4,damithc/addressbook-level4,se-edu/addressbook-level3,damithc/addressbook-level4