Re: tests in log-scale plots

[John W. Eaton]

On  6-Sep-2011, Kai Habel wrote:

| you are right, I think a lot of test are possible for the graphic
| function when using a hidden figure. I have recently commited some
| test for the scripts in the plot directory.
| 
| Take a look at: http://hg.savannah.gnu.org/hgweb/octave/rev/5553412c6614
| e.g. line.m

Things like this are OK if they are actually testing something.  But
I think we should avoid relying on tests like

  %!test
  %! figure (1, 'visible', 'off')
  %! clf ();
  %! plot (something);

Sure, this tests that the plot function executes without error, but it
doesn't tell us anything about whether the plot is correct.

Also, not that we should cover up bugs, but weren't there problems
with using "figure (1, 'visible', 'off')" with the OpenGL+FLTK
plotting?  It seems to work for me now, but I remember a bug report
about this and I don't remember it being fixed for everyone.

jwe