Sometimes it is useful to have a Pwl with only a single point defined.
A practical use case is tuning files with only a single entry for Pwl
related parameters, where the expectation is that this entry just gets
used.
Add a failing test case for such a single point Pwl.
Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
e33814c65b