r devtools test() errors but testthat test_file() works - r

Question

I have a function in a package I'm building that assigns a hex-code to the global environment for use by analysts...
optiplum<-function(){
assign(
x="optiplum",
value=rgb(red=129,green=61,blue=114, maxColorValue = 255),
envir=.GlobalEnv)
}
My unit test code is:
test_that("optiplum - produces the correct hex code",{
optiplum()
expect_true(identical(optiplum,"#813D72"))
})
When I run the code manually, there isn't an error:
> str(optiplum)
chr "#813D72"
> str("#813D72")
chr "#813D72"
> identical("#813D72",optiplum)
[1] TRUE
> expect_true(identical(optiplum,"#813D72"))
When I run a test_file() is also does not error
> test_file("./tests/testthat/test-optiplum.R")
optiplum : .
However, when I run the test as part of my devtools workflow:
> test()
Testing optINTERNAL
Loading optINTERNAL
optiplum : 1
1. Failure: optiplum - produces the correct hex code --------------------------------------------------------------------------------------------------------------
identical(optiplum, "#813D72") isn't true
Anyone have any ideas on why this might be occurring and how I can resolve the situation?

Answer 1

Assignment to the global environment is a no-no, see R Inferno and testthat isolates tests as much as possible (see test_that() details). As a consequence, the optiplum() assignment to the global environment would not succeed because the testthat function strictly prohibits such behaviour.
#Hadley rightly points out that the function should just return the string instead of assigning it, particularly since it is just two extra characters for each use.
So not
optiplum<-function(){
assign(
x="optiplum",
value=rgb(red=129,green=61,blue=114, maxColorValue = 255),
envir=.GlobalEnv)
}
but
optiplum <- function() rgb(red=102,green=17,blue=109, maxColorValue = 255)