R devel - Feb 2015 - Testthat and global environments in R packages on CRAN

Hi!

Im currently developing an R package to automatically give students
feedback on programming assignments in R. I use the testthat package as an
engine for the unit testing and do a wrapper to make the automatic marking
easy for the students.

One function (called mark_my_file() ) will mark the students lab file using
testthat tests and a new (simple) reporter. The problem is that I need to
do the marking of the lab with an empty global environment (due to the
testthat package).

So my first thought was to:
1) store the global environement in the temporary directory as an
.Rdata-file
2) clean the global environment
3) run the tests
4) clean the global environment (from the student lab file)
5) reload the old global environment

But the problem is that it is not possible to publish packages on CRAN that
modifies the global environment.

Is there anyone that have any solutions/ideas to this problem?

The package can be found here:
https://github.com/MansMeg/markmyassignment

-- 
Kind regards

M?ns

===========================M?ns Magnusson
+46 (0) 70 588 97 15
mons.magnusson at gmail.com
===========================
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On 08/02/2015 8:22 AM, M?ns Magnusson wrote:
> Hi!
> 
> Im currently developing an R package to automatically give students
> feedback on programming assignments in R. I use the testthat package as an
> engine for the unit testing and do a wrapper to make the automatic marking
> easy for the students.
> 
> One function (called mark_my_file() ) will mark the students lab file using
> testthat tests and a new (simple) reporter. The problem is that I need to
> do the marking of the lab with an empty global environment (due to the
> testthat package).
> 
> So my first thought was to:
> 1) store the global environement in the temporary directory as an
> .Rdata-file
> 2) clean the global environment
> 3) run the tests
> 4) clean the global environment (from the student lab file)
> 5) reload the old global environment
> 
> But the problem is that it is not possible to publish packages on CRAN that
> modifies the global environment.
> 
> Is there anyone that have any solutions/ideas to this problem?
> 
> The package can be found here:
> https://github.com/MansMeg/markmyassignment
> 
I don't think that testthat requires you to use the global environment.
 Could you give some example code to show where you think you need it?
Someone could probably come up with a different formulation.

Duncan Murdoch

Hi!

The problem is that the test environment inherits from the global environment.
See https://github.com/hadley/testthat/blob/master/R/test-files.r

The students labs are simply an R script file. Say that they have an assignment
to calculate sqrt(2) and store it in variable a. In the same session they should
be able to test the script file when they are done (using a function
mark_my_file() in the package). This function will call the testthat tests.

Say that I have two unit tests. One tests if an object called 'a' exists
in the file and the second one tests if 'a' is sqrt(2) and return
messages to the students pointing them in the right direction (ie 'a' is
missing or is wrong).

The problem is the if the student have an other object 'a' in the global
environment but do not create 'a' in their R script file. In this case
testthat test will follow the search path and find the object in the global
environment and return the wrong (or none) error message due to the global
environment.

The only way around this problem is to temporarily store the global environment,
clean it and run the tests, and the reload the old global environment. But this
solution will not be publishable on CRAN.

I hope this can clarify the problem.

Kind regards
M?ns



Skickat fr?n min iPhone
> 8 feb 2015 kl. 16:46 skrev Duncan Murdoch <murdoch.duncan at
gmail.com>:
> 
>> On 08/02/2015 8:22 AM, M?ns Magnusson wrote:
>> Hi!
>> 
>> Im currently developing an R package to automatically give students
>> feedback on programming assignments in R. I use the testthat package as
an
>> engine for the unit testing and do a wrapper to make the automatic
marking
>> easy for the students.
>> 
>> One function (called mark_my_file() ) will mark the students lab file
using
>> testthat tests and a new (simple) reporter. The problem is that I need
to
>> do the marking of the lab with an empty global environment (due to the
>> testthat package).
>> 
>> So my first thought was to:
>> 1) store the global environement in the temporary directory as an
>> .Rdata-file
>> 2) clean the global environment
>> 3) run the tests
>> 4) clean the global environment (from the student lab file)
>> 5) reload the old global environment
>> 
>> But the problem is that it is not possible to publish packages on CRAN
that
>> modifies the global environment.
>> 
>> Is there anyone that have any solutions/ideas to this problem?
>> 
>> The package can be found here:
>> https://github.com/MansMeg/markmyassignment
> 
> I don't think that testthat requires you to use the global environment.
> Could you give some example code to show where you think you need it?
> Someone could probably come up with a different formulation.
> 
> Duncan Murdoch
> 
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