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(), msg = NULL) see_if(..., env = parent.frame(), msg = NULL)
... |
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. |
msg |
a custom error message to be printed if one of the conditions is false. |
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
. Alternatively, a custom message
can be specified for each call.
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)) assert_that(FALSE, msg = "Custom error message") ## 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")) see_if(5 < 3, msg = "Five is not smaller than three")