assert_that {assertthat} | R Documentation |
assert_that
is a drop-in replacement for stopifnot
but
is designed to give informative error messages.
assert_that(..., env = parent.frame()) see_if(..., env = parent.frame())
... |
unnamed expressions that describe the
conditions to be tested. Rather than combining
expressions with |
env |
(advanced use only) the environment in which to evaluate the assertions. |
Assertion functions should return a single TRUE
or
FALSE
: any other result is an error, and
assert_that
will complain about it. This will
always be the case for the assertions provided by
assertthat
, but you may need be a more careful for
base R functions.
To make your own assertions that work with
assert_that
, see the help for
on_failure
.
validate_that
, which returns a message (not an error)
if the condition is false.
x <- 1 # assert_that() generates errors, so can't be usefully run in # examples ## Not run: assert_that(is.character(x)) assert_that(length(x) == 3) assert_that(is.dir("asdf")) y <- tempfile() writeLines("", y) assert_that(is.dir(y)) ## End(Not run) # But see_if just returns the values, so you'll see that a lot # in the examples: but remember to use assert_that in your code. see_if(is.character(x)) see_if(length(x) == 3) see_if(is.dir(17)) see_if(is.dir("asdf"))