Turn a Check into an Assertion

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Description

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).

Usage

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makeAssertion(x, res, var.name, collection)

makeAssertionFunction(check.fun, c.fun = NULL, env = parent.frame())

Arguments

x

[any]
Object to check.

res

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

var.name

[character(1)]
The custom name for x as passed to any assert* function. Defaults to a heuristic name lookup.

collection

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

check.fun

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

c.fun

[character(1)]
If not NULL, instead of calling the function check.fun, use .Call to call a C function “c.fun” with the identical set of parameters. The C function must be registered as a native symbol, see .Call. Useful if check.fun is just a simple wrapper.

env

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

Value

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

Examples

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

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

# Alternative: Automatically create such a function
assertFalse = makeAssertionFunction(checkFalse)
print(assertFalse)

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