Use of environment in validate_that in R - r

Question

I am trying to write my own test-function (test_if) that returns both the result of the test as well as an optional error message. The function is based on the validate_that function in the assertthat-package.
The test_if function seems to work, however, I further want to use test_if in a more specific function (check_input) that analyses user-inputs in shiny. There I have a problem, that the check_input-function only works, if I define the test_if function inside the check_input function.
I suppose that the problem is caused by some search scope or environment problem. However, I am really a newbie to environments in R.
How can I get my check_input-function work without the need to define the test_if function inside it?
Many thanks, Silke
Here is my minimal working example:
library(assertthat)
test_if <- function(...,msg=NULL) {
test <- validate_that(...,msg=msg)
if (is.logical(test)) {
return(list(assertation=test,msg=NULL))
}
if (is.character(test)) {
return(list(assertation=FALSE,msg=test))
}
}
test_if(2==3)
test_if(3==3)
test_if(2==3,3==4,msg="something is wrong")
### To check different inputs
check_input1 <- function(value1 = NULL,value2 = NULL) {
test_if <- function(...,msg=NULL) {
test <- validate_that(...,msg=msg)
if (is.logical(test)) {
return(list(assertation=test,msg=NULL))
}
if (is.character(test)) {
return(list(assertation=FALSE,msg=test))
}
}
error_msg <- ""
error_status <- FALSE
check <- test_if(is.numeric(value1))
error_msg <- check$msg
error_status <- check$assertation
return(list(error_msg=error_msg,error_status=error_status))
}
check_input2 <- function(value1 = NULL,value2 = NULL) {
error_msg <- ""
error_status <- FALSE
check <- test_if(is.numeric(value1))
error_msg <- check$msg
error_status <- check$assertation
return(list(error_msg=error_msg,error_status=error_status))
}
check_input1(value1=1)
check_input2(value1=1)