On Tue, Oct 4, 2016 at 4:55 PM, Anna Petrášová <kratocha...@gmail.com> wrote:
> [...] > c) test correctness of results. > It just depends how you write them, and yes, for some modules c) is > more difficult to implement than for others. > On Thu, Oct 6, 2016 at 5:00 PM, Anna Petrášová <kratocha...@gmail.com> wrote: > There is correct result in the sense "as author intended". So you can > use pen and paper and solve very small example. That doesn't mean it > will cover all options, but better than nothing. [...] > For r.forestfrag, I wrote a test which was based on an example in the original paper which was computing value of one cell in 3x3 window. It is a really trivial example which tests 1 number and two other numbers which are intermediate results. However, by writing it, I actually discovered that although the results for a large area look good, this small example, which I was able compute by hand, is failing. After investigation, it turned out that the error is actually in r.mapcalc. Computing the result outside of GRASS was crucial in this case. It was an index and I was able to compute it by hand (and check it with the example in the paper). For some other modules it could be more difficult and I don't want to compute it without GRASS for more than one cell even in this case, but it was certainly possible to write a test of correctness for this module. Note that the test doesn't show if the (forest fragmentation) index makes sense or if it is useful, but it shows that the module gives the result it promised. This is the original test: https://trac.osgeo.org/grass/browser/grass-addons/grass7/raster/r.forestfrag/testsuite/r_forestfrag_trivial.py This is the r.mapcalc bug: https://trac.osgeo.org/grass/ticket/3067 And this is test which specifically shows the bug (would show if it would be reintroduced): https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.mapcalc/testsuite/test_row_above_below_bug.py
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