With the addition of :window-only, it's no longer necessary to use
"Given I have a fresh instance" to clean up previous windows. This
greatly cuts down on the amount of process restarts that need to happen
to complete a full testing cycle.
I also made one of the tests more robust against order alterations, and
removed some unnecessary extra commands that were already implied by the
background on others.
The test for inserting text at a specific position failed because
<Ctrl+Right> doesn't behave the same on Windows and Linux. This changes
it to move the cursor using other keys.
Changes :yank's flag arguments to a positional "what" argument
specifying the object to be yanked. Including "selection" as a
possibility allows for the replacement of :yank-selected with
:yank selection.
