nested warnings & messages with testthat

test.R

f <- function() {
  warning('a warning')
  message('a message')
}
g <- function() {
  withCallingHandlers(
    warning = function(cnd) {
      message('oh no, a warning occurred')
    },
    warning('a warning')
  )
}
test_that("f() warning & message", {
  expect_warning(expect_message(f(), 'a message'), 'a warning')
})
test_that("g() handles warning with a message", {
  expect_warning(expect_message(g(), 'oh no'), 'a warning')
})