Re: Regression Testing of Graphics: some questions

*To*: mathgroup at smc.vnet.net*Subject*: [mg128123] Re: Regression Testing of Graphics: some questions*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Mon, 17 Sep 2012 00:23:08 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20120916072514.963746863@smc.vnet.net>

Why use cut-and-paste? graf := ListPlot[{1, 2, 2, 3}, ImageSize -> Tiny]; previousResult = graf; Head[previousResult] Graphics previousResult === graf True test[expr_, ansr_] := expr === ansr; test[graf, previousResult] True Bob Hanlon On Sun, Sep 16, 2012 at 3:25 AM, James Stein <mathgroup at stein.org> wrote: > > To my surprise, if you copy a Graphic from a notebook and paste it > elsewhere in the notebook, the Graphic objects are not the same (even > though their visual appearance is identical. > > I discovered this irritation attempting regression testing. Here's an > example: assume you have a function 'test' that takes two arguments: > test [ expression_, expectedResult _] > An overly simple implementation might be this: > SetAttributes [ test, HoldAll ] ; > test [ expr_, ansr_ ] := expr === ansr; > Now suppose you wish to verify that some routine, say 'graf', is still > giving the same result it it did previously. Here is an example: > > graf := ListPlot [ { 1, 2, 2, 3 }, ImageSize->Tiny ]; > test [ graf , previousResult ] // Print; > > What should 'previousResult' be? You might consider copying the graphic > produced by 'graf' earlier, which was correct, and paste it into 'test' as > the second argument. Unfortunately, the action of copy & paste changes the > internal structure of Graphic [ a1, a2, ... ] so the regression test will > always fail. > > Questions: > (1) Is there a good reason for this? (The unwashed are curious.) > (2) Is this a bug (or 'feature') that could be fixed? > (3) Is there a way to prevent it? > (4) Is there an algorithm to do one of > (a) convert an original Graphic to its pasted form. > (b) convert a pasted Graphic to its original form. > (c) convert any Graphic to a canonical form, such that any two Graphic > objects that produce identical displays will have identical canonical forms. > > For the truly curious, here are the differences in for a rather simple > ListPlot I made. Let OG be the original, and CG be the pasted copy of OG. > > OG had Length 2; CG had Length 8. > > OG [[ 1 ]] was { { { }, {Hue[0.67, 0.6, 0.6], Point[{{1., 1.}, {2., 2.}, > {3., 2.}, {4., 3.}}]}, { } } } > CG [[ 1 ]] was { { }, {Hue[0.67, 0.6, 0.6], Point[{{1., 1.}, {2., 2.}, > {3., 2.}, {4., 3.}}]}, { } } > > OG [ [ 2 ] ] was List of seven rules, > > OG [ [ 2 through 8 ] ] were the same seven rules. > > It would be simple to convert one of these trees to the other, but it would > be rash to generalize the nature of the needed conversion without extensive > investigations. Perhaps a Wolfram wizzard can throw light on these > questions, or someone can propose a different kind of regression testing to > skirt the issue? > >

**References**:**Regression Testing of Graphics: some questions***From:*James Stein <mathgroup@stein.org>