Smart Key - ERT Results Mode

When in an Emacs Regression Test (ERT) results buffer:
  ACTION KEY
     Filters ert-results-mode test results entries to those
     matching the result status of the entry at point.  Does nothing
     if there is no entry at point.

     With point on any of the statistics lines in the top section of the
     results buffer, does the following:
       Selector: - toggles showing/hiding all test results
       Passed:   - shows passed tests only
       Failed:   - shows failed tests only
       Skipped:  - shows skipped tests only
       Total:    - shows all tests
  ASSIST KEY
     Displays help documentation for the ert-results-mode test at point,
     if any.  Triggers an error if there is no test result at or before point."

There are also drag actions that work on delimited things.  If no
region is selected, when the Action Mouse Key is dragged from a thing
delimiter to another location, it copies the thing and yanks it at the
new location.  Similarly, the Assist Mouse Key kills the thing at its
original location and yanks it at the new location.