Unit Testing Frameworks: summary and brief discussion

Greetings -

I'm finally finished review, here's what I heard:

============ from Tobias Verbeke:

anthony.rossini at novartis.com wrote:

Greetings!

After a quick look at current programming tools, especially with regards 

to unit-testing frameworks, I've started looking at both "butler" and 
"RUnit".   I would be grateful to receieve real world development 
experience and opinions with either/both.    Please send to me directly 
(yes, this IS my work email), I will summarize (named or anonymous, as 
contributers desire) to the list.

I'm founding member of an R Competence Center at an international 
consulting company delivering R services
mainly to the financial and pharmaceutical industries. Unit testing is 
central to our development methodology
and we've been systematically using RUnit with great satisfaction, 
mainly because of its simplicity. The
presentation of test reports is basic, though. Experiences concerning 
interaction with the RUnit developers
are very positive: gentle and responsive people.

We've never used butler. I think it is not actively developed (even if 
the developer is very active).

It should be said that many of our developers (including myself) have 
backgrounds in statistics (more than in cs
or software engineering) and are not always acquainted with the 
functionality in other unit testing frameworks
and the way they integrate in IDEs as is common in these other languages.

I'll soon be personally working with a JUnit guru and will take the 
opportunity to benchmark RUnit/ESS/emacs against
his toolkit (Eclipse with JUnit- and other plugins, working `in perfect 
harmony' (his words)). Even if in my opinion the
philosophy of test-driven development is much more important than the 
tools used, it is useful to question them from
time to time and your message reminded me of this... I'll keep you 
posted if it interests you. Why not work out an
evaluation grid / check list for unit testing frameworks ?

Totally unrelated to the former, it might be interesting to ask oneself 
how ESS could be extended to ease unit testing:
after refactoring a function some M-x ess-unit-test-function 
automagically launches the unit-test for this particular
function (based on the test function naming scheme), opens a *test 
report* buffer etc.

Kind regards,
Tobias

============ from Tony Plate:

Hi, I've been looking at testing frameworks for R too, so I'm interested 
to hear of your experiences & perspective.

Here's my own experiences & perspective:
The requirements are:

(1) it should be very easy to construct and maintain tests
(2) it should be easy to run tests, both automatically and manually
(3) it should be simple to look at test results and know what went wrong 
where

I've been using a homegrown testing framework for S-PLUS that is loosely 
based on the R transcript style tests (run *.R and compare output with 
*.Rout.save in 'tests' dir).  There are two differences between this 
test framework and the standard R one:
(1) the output to match and the input commands are generated from an 
annotated transcript (annotations can switch some tests in or out 
depending on the version used)
(2) annotations can include text substitutions (regular expression 
style) to be made on the output before attempting to match (this helps 
make it easier to construct tests that will match across different 
versions that might have minor cosmetic differences in how output is 
formatted).

We use this test framework for both unit-style tests and system testing 
(where multiple libraries interact and also call the database).
One very nice aspect of this framework is that it is easy to construct 
tests -- just cut and paste from a command window.  Many tests can be 
generated very quickly this way (my impression is that is is much much 
faster to build tests by cutting and pasting transcripts from a command 
window than it is to build tests that use functions like all.equal() to 
compare data structures.) It is also easy to maintain tests in the face 
of change (e.g., with a new version of S-PLUS or with bug fixes to 
functions or with changed database contents) -- I use ediff in emacs to 
compare test output with the stored annotated transcript and can usually 
just use ediff commands to update the transcript.

This has worked well for us and now we are looking at porting some code 
to R.  I've not seen anything that offers these conveniences in R.

It wouldn't be too difficult to add these features to the built-in R 
testing framework, but I've not had success in getting anyone in R core 
to listen to even consider changes, so I've not pursued that route after 
an initial offer of some simple patches to tests.mk and wintests.mk.

RUnit doesn't have transcript-style tests, but it wasn't very difficult 
to add support for transcript-style tests to it.  I'll probably go ahead 
and use some version of that for our porting project.  (And offer it to 
the community if the RUnit maintainers want to incorporate it.)  I also 
like the idea that RUnit has some code analysis tools -- that might 
support some future project that allowed one to catalogue the number of 
times each code path through a function was exercised by the tests.

I just looked at 'butler' and it looks very much like RUnit to me -- and 
I didn't see any overview that explained differences.  Do you know of 
any differences?

cheers,

Tony Plate


============== from Paul Gilbert:

Tony

While this is not exactly your question, I have been using my own system 
  based on make and the tools use by R CMD build/check to do something I 
think of as unit testing. This pre-dates the unit-testing frameworks, in 
fact, some of it predates R. I actually wrote something on this at one 
point: Paul Gilbert. R package maintenance. R News, 4(2):21-24, 
September 2004.

I have occasionally thought about trying to use RUnit, but never done 
much because I am relatively happy with what I have. (Inertia is an 
issue too.)  I would be happy to hear if you do an assessment of the 
various tools.

Best,
Paul Gilbert


============= From Seth Falcon:

Hi Tony,

anthony.rossini at novartis.com writes:

After a quick look at current programming tools, especially with regards 

to unit-testing frameworks, I've started looking at both "butler" and 
"RUnit".   I would be grateful to receieve real world development 
experience and opinions with either/both.    Please send to me directly 
(yes, this IS my work email), I will summarize (named or anonymous, as 
contributers desire) to the list.

I've been using RUnit and have been quite happy with it.  I had not
heard of butler until I read your mail (!).

RUnit behaves reasonably similarly to other *Unit frameworks and this
made it easy to get started with as I have used both JUnit and PyUnit
(unittest module).

Two things to be wary of:

  1. At last check, you cannot create classes in unit test code and
     this makes it difficult to test some types of functionality.  I'm
     really not sure to what extent this is RUnit's fault as opposed
     to limitation of the S4 implemenation in R.

  2. They have chosen a non-default RNG, but recent versions provide a
     way to override this.  This provided for some difficult bug
     hunting when unit tests behaved differently than hand-run code
     even with set.seed().

The maintainer has been receptive to feedback and patches.  You can
look at the not-so-beautiful scripts and such we are using if you look
at inst/UnitTest in: Category, GOstats, Biobase, graph

Best Wishes,

+ seth


=================== Discussion:

After a bit more cursory use, it looks like RUnit is probably the right 
approach at this time (sorry Hadley!).   Both RUnit and butler have a 
range of testing facilities and programming support tools.   I support the 
above statements about feasibility and problems -- except that I didn't 
get a chance to checkout the S4 issues that Seth raised above.    The one 
piece that I found missing in my version was some form of GUI based 
tester, i.e. push a button and test, but I think I've not thought through 
some of the issues with environments and closures yet that might cause 
problems.

Thanks to everyone for responses!  It's clear that there is a good start 
here, but lots of room for improvement exists.

Best regards / Mit freundlichen Gr?ssen, 
Anthony (Tony) Rossini
Novartis Pharma AG
MODELING & SIMULATION
Group Head a.i., EU Statistical Modeling
CHBS, WSJ-027.1.012
Novartis Pharma AG
Lichtstrasse 35
CH-4056 Basel
Switzerland
Phone: +41 61 324 4186
Fax: +41 61 324 3039
Cell: +41 79 367 4557
Email : anthony.rossini at novartis.com

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