The two main functionalities of this package are creating mock objects
(functions) and selectively intercepting calls to a given function that
originate in some other function. It can be used with any testing framework
available for R. Mock objects can be injected with either this package's own
stub() function or a similar with_mock() facility present in the 'testthat'
package.

WWW: https://github.com/jfiksel/mockery