testthat::test_that() : output of utils::capture.output() is different outside and inside testthat::test_that()

[gael-millot]

Hello.

I do not understand this behavior. Is it a bug ?
If not, how to solve this?
Thanks !
Gael.

In the follwing code, print(output) should return "HELLO", not character(0):

testthat::test_that(
    desc = "get_message", 
    code = {
        output <- utils::capture.output(
            message('HELLO'),
            type = "message"
        )
        print(output)
    }
)

character(0)
── Skip: get_message ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Reason: empty test

output <- utils::capture.output(
    message('HELLO'),
    type = "message"
)
print(output)

[1] "HELLO"

Another more complicate example:

fun1 <- function(data){
    output <- utils::capture.output(
        base::suppressWarnings(expr = base::eval(expr = base::parse(text = data)), classes = "warning"),
        type = "message"
    )
    return(output)
}
str2 <- "message('HELLO')"
a <- fun1(str2)
print(a)

[1] "HELLO"

testthat::test_that(
    desc = "get_message", 
    code = {
        str2 <- "message('HELLO')"
        a <- fun1(str2)
        print(a)
    }
)
# or testthat::test_that(desc = "get_message", code = print(fun1(str2)))

character(0)
── Skip: get_message ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Reason: empty test

[gael-millot]

Here, results are not different:

fun2 <- function(data){
    output <- base::eval(expr = base::parse(text = data))
    return(output)
}
str2 <- "sum(1:3)"
a <- fun2(str2)
print(a)

[1] 6

testthat::test_that("get_message()", {
    a <- fun2(str2)
    print(a)
})

[1] 6
── Skip: get_message() ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Reason: empty test