makeExpectation is the internal function used to evaluate the result of a check and turn it into an expectation. makeExceptionFunction can be used to automatically create an expectation function based on a check function (see example).

makeExpectation(x, res, info, label)

makeExpectationFunction(, = NULL,
  use.namespace = 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.


See expect_that


See expect_that

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.


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


makeExpectation invisibly returns the checked object.

makeExpectationFunction returns a function.

See also

Other CustomConstructors: makeAssertion(), makeTest()


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

# Create the respective expect function
expect_false = function(x, info = NULL, label = vname(x)) {
  res = checkFalse(x)
  makeExpectation(x, res, info = info, label = label)

# Alternative: Automatically create such a function
expect_false = makeExpectationFunction(checkFalse)
#> function (x, info = NULL, label = vname(x)) 
#> {
#>     if (missing(x)) 
#>         stop(sprintf("Argument '%s' is missing", label))
#>     res = checkFalse(x)
#>     makeExpectation(x, res, info, label)
#> }
#> <environment: 0x560118fbf960>