makeAssertion is the internal function used to evaluate the result of a check and throw an exception if necessary. makeAssertionFunction can be used to automatically create an assertion function based on a check function (see example).

makeAssertion(x, res,, collection)

makeAssertionFunction(, = NULL,
  use.namespace = TRUE,
  coerce = FALSE,
  env = parent.frame()



Object to check.


[TRUE | character(1)]
The result of a check function: TRUE for successful checks, and an error message as string otherwise.

The custom name for x as passed to any assert* function. Defaults to a heuristic name lookup.


If an AssertCollection is provided, the error message is stored in it. If NULL, an exception is raised if res is not TRUE.

Function which checks the input. Must return TRUE on success and a string with the error message otherwise.

If not NULL, instead of calling the function, use .Call to call a C function “” with the identical set of parameters. The C function must be registered as a native symbol, see .Call. Useful if is just a simple wrapper.


Call functions of checkmate using its namespace explicitly. Can be set to FALSE so save some microseconds, but the checkmate package needs to be imported. Default is TRUE.


If TRUE, injects some lines of code to convert numeric values to integer after an successful assertion. Currently used in assertCount, assertInt and assertIntegerish.


The environment of the created function. Default is the parent.frame.


makeAssertion invisibly returns the checked object if the check was successful, and an exception is raised (or its message stored in the collection) otherwise.

makeAssertionFunction returns a function.

See also

Other CustomConstructors: makeExpectation(), makeTest()


# Simple custom check function
checkFalse = function(x) if (!identical(x, FALSE)) "Must be FALSE" else TRUE

# Create the respective assert function
assertFalse = function(x, = vname(x), add = NULL) {
  res = checkFalse(x)
  makeAssertion(x, res,, add)

# Alternative: Automatically create such a function
assertFalse = makeAssertionFunction(checkFalse)
#> function (x, = checkmate::vname(x), add = NULL) 
#> {
#>     if (missing(x)) 
#>         stop(sprintf("argument \"%s\" is missing, with no default", 
#>     res = checkFalse(x)
#>     checkmate::makeAssertion(x, res,, add)
#> }
#> <environment: 0x56011a607770>