assert_that is a drop-in replacement for
is designed to give informative error messages.
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unnamed expressions that describe the conditions to be tested.
Rather than combining expressions with
(advanced use only) the environment in which to evaluate the assertions.
a custom error message to be printed if one of the conditions is false.
Assertion functions should return a single
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
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.
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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")
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