How to mute messages and warnings with testthat when they are expected

In order to develop a package, I am using testthat. I want to test if my functions send proper messages and warnings. I want to test the results of functions at the same time. This is how I am trying to do it:

## R/foo.r
foo <- function() {
  message("This is a message")
  warning("This is a warning")
  "This is a result"
}

I write these tests:

## tests/testthat/test-foo.R

test_that("foo works", {
  expect_equal(foo(), "This is a result")
  expect_message(foo(), "This is a message")
  expect_warning(foo(), "This is a warning")
})

But now when I run the tests I have this:

Loading testWarnMess
Testing testWarnMess
v |  OK F W S | Context
/ |   0       | foo                                                                           This is a message
v |   3   2   | foo [0.3 s]                                                                   
----------------------------------------------------------------------------------------------
Warning (test-foo.R:2:3): foo works
This is a warning
Backtrace:
 1. testthat::expect_equal(foo(), "This is a result") test-foo.R:2:2
 4. testWarnMess::foo()

Warning (test-foo.R:3:3): foo works
This is a warning
Backtrace:
 1. testthat::expect_message(foo(), "This is a message") test-foo.R:3:2
 7. testWarnMess::foo()
----------------------------------------------------------------------------------------------

== Results ===================================================================================
Duration: 0.3 s

[ FAIL 0 | WARN 2 | SKIP 0 | PASS 3 ]
This is a message

How to prevent messages and warnings to be seen in the test results when I am expecting them to happen?

One great way to do that is to use the adverb purrr::quietly.

test_that("foo works", {
  qfoo <- purrr::quietly(foo)
  qfoo_call <- qfoo()
  expect_equal(qfoo_call$result, "This is a result")
  expect_equal(qfoo_call$message, "This is a message")
  expect_equal(qfoo_call$warning, "This is a warning")
})