clear_warnings <- function() last.warning <<- list()

careless <- function(f) {
    function(...) {
        suppressWarnings(f(...))
    }
}

fail_with <- function(expr, value) tryCatch(expr, error = function(cond) value)
does_error <- function(expr) {
    didFail <- F
    tryCatch(expr, error = function(cond) didFail <<- T)
    didFail
}

count_warnings <- function(expr) {
    N <- 0
    withCallingHandlers(expr, warning = function(cond) N <<- N + 1)
    N
}

record <- function(expr) {
    msgs <- c()
    rec <- function(cond) { msgs <<- c(msgs, cond$message); rlang::cnd_muffle(cond)}
    withCallingHandlers(expr, warning = rec, message = rec)
    msgs
}