Test Expand/Collapse Filters
========================
This test shows that the expand/collapse arrow of a filter category
header works well.

#. Open the dash.
#. Make sure that a collapse arrow is shown adjacent to every
   filter category header.
#. Click on it.
#. The filter category should collapse.
#. Make sure that an expand arrow is shown ajacent to every filter
   category header.
#. Click on it (again).
#. The filter category should expand.


Test no-over-state effect
=========================
This test show that filter buttons in the Dash do not have a mouse
over state.

#. Open the dash.
#. Move the mouse on filter buttons.

Outcome
  The filter buttons have no mouseover state effect.