Testing warnings in R by comparing strings (best idea?) -

i'm working on r package , need writing r test functions meant check whether correct warning being thrown on c-side code , caught on r side. let me give background on i'm working on exactly:

1. most of i'm writing done on c side. in addition, have if-statement type macro in c allows coder pass warning r in form of string. basic premise if(statement_true) pass_warning_to_r("warning string pass"). i'd test whether these warnings being thrown when expect/need them writing r file uses trycatch blocks.

2. so far i've written similar this:

   counter <- 0 trycatch({  function_im_testing()  }, warning = function(war) {      # check if warning expected , if increment counter      if(tostring(war)=="the warning i'm expecting/testing for"){         print(tostring(war))         counter <- counter + 1      }  }, error = function(err) {       print(tostring(err))  }, = { print("leaving trycatch") })  # stop if 3 warnings expected aren't present stopifnot(counter == 3) 

this method i'm using and, far, haven't been able if statement execute trying tostring(war) , "warning i'm expecting/testing for" same thing. this, in addition fact method pretty sloppy , unreliable, leads me believe there's better way. so, there better approach doing this?

usually warnings you'd allow evaluation continue; trycatch used stop evaluation. instead use withcallinghandlers handler warnings want, , invokes 'mufflewarning' restart. message of error / warning can extracted conditionmessage

counter <- 0l withcallinghandlers({     function_im_testing() }, warning = function(w) {     if (conditionmessage(w) == "the warning i'm expecting/testing for")         counter <<- counter + 1l     invokerestart("mufflewarning") }) 

since you're writing own package, makes sense create warnings can identified in more robust way, e.g., following returns condition can used in warning, has class 'bad_input' can used in withcallinghandlers.

bad_input <- function(...) {     w <- simplewarning(...)     class(w) <- c("bad_input", class(w))     w } 

to used warning(bad_input("your input bad")) , producing output with

fun <- function() {     warning("oops")     warning(bad_input("your input bad"))     "done" }         

like

>     fun() [1] "done" warning messages: 1: in fun() : oops 2: input bad  >     counter <- 0l >     withcallinghandlers(fun(), bad_input = function(w) { +         counter <<- counter + 1l +         invokerestart("mufflewarning") +     }) [1] "done" warning message: in fun() : oops > counter [1] 1