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Message-ID: <1df17415-0a48-a1a2-6498-6af12419f346@gmail.com>
Date: 2021-04-16T10:08:58Z
From: Duncan Murdoch
Subject: [R-pkg-devel] Problems with too much testing

I'm updating the rgl package, and have come across the following problem.

Some packages that depend on rgl and do careful testing are detecting 
inconsequential changes.  A typical case is the nat package, which has 
extensive testing, some of which comes down to checking results from rgl 
functions using testthat::is_equal().  I rewrote some parts of the rgl 
code, and so some rgl objects differ in irrelevant ways.  For example,

   obj <- list(x = NULL)

differs from

   obj <- list()
   obj[["x"]] <- NULL

(the first is length 1, the second ends up with no entries).  All tests 
in rgl would be like

   if (is.null(obj[["x"]])) ...

so the tests evaluate the same, but testthat::is_equal() doesn't return 
TRUE, because the objects are different.

Another example would be

   obj <- list()
   obj$a <- 1
   obj$b <- 2

which differs from

   obj <- list()
   obj$b <- 2
   obj$a <- 1

in the order of the components, but since rgl always accessed them by 
name, that makes no difference.

So what I'm looking for is a strategy to hide internal implementation 
details.  (I'm using a compare_proxy() method now which standardizes the 
objects, but that seems very specific to testthat version 3.  I'd like 
ideas for something more robust.)

Duncan Murdoch