Title: | Mocking in R |
---|---|
Description: | Provides a means to mock a package function, i.e., temporarily substitute it for testing. Designed as a drop-in replacement for the now deprecated 'testthat::with_mock()' and 'testthat::local_mock()'. |
Authors: | Kirill Müller [aut, cre] |
Maintainer: | Kirill Müller <[email protected]> |
License: | GPL-3 |
Version: | 0.2.0.9002 |
Built: | 2024-11-08 02:41:23 UTC |
Source: | https://github.com/mrc-ide/mockr |
Called by default from with_mock()
to determine
the environment where to update mocked functions.
This function is exported to help troubleshooting.
get_mock_env(.parent = parent.frame())
get_mock_env(.parent = parent.frame())
.parent |
|
This function works differently depending on
testthat::is_testing()
.
Outside testthat, topenv(.parent)
is returned.
This was the default for mockr < 0.1.0 and works for many cases.
In testthat, asNamespace("<package>")
for the tested package is returned.
The tested package is determined via testthat::testing_package()
.
If this is empty (e.g. if a test_that()
block is run in interactive mode),
this function looks in the search path for packages loaded by
pkgload::load_all()
.
local_mock()
temporarily substitutes implementations of package functions.
This is useful for testing code that relies on functions that are
slow, have unintended side effects or access resources that may not be
available when testing.
with_mock()
substitutes, runs code locally, and restores in one go.
local_mock( ..., .parent = parent.frame(), .env = get_mock_env(.parent), .defer_env = parent.frame() ) with_mock(..., .parent = parent.frame(), .env = get_mock_env(.parent))
local_mock( ..., .parent = parent.frame(), .env = get_mock_env(.parent), .defer_env = parent.frame() ) with_mock(..., .parent = parent.frame(), .env = get_mock_env(.parent))
... |
|
.parent |
|
.env |
|
.defer_env |
|
This works by adding a shadow environment as a parent of the environment
in which the expressions are evaluated. Everything happens at the R level,
but only functions in your own package can be mocked.
Otherwise, the implementation is modeled after the original version in the
testthat
package, which is now deprecated.
local_mock()
returns NULL
, invisibly.
with_mock()
returns the result of the last unnamed argument.
Visibility is preserved.
Suraj Gupta (2012): How R Searches And Finds Stuff
some_func <- function() stop("oops") some_other_func <- function() some_func() my_env <- environment() tester_func <- function() { # The default for .env works well most of the time, # unfortunately not in examples local_mock(some_func = function() 42, .env = my_env) some_other_func() } try(some_other_func()) tester_func() tester_func_with <- function() { with_mock( some_func = function() 42, .env = my_env, { some_other_func() } ) } tester_func_with()
some_func <- function() stop("oops") some_other_func <- function() some_func() my_env <- environment() tester_func <- function() { # The default for .env works well most of the time, # unfortunately not in examples local_mock(some_func = function() 42, .env = my_env) some_other_func() } try(some_other_func()) tester_func() tester_func_with <- function() { with_mock( some_func = function() 42, .env = my_env, { some_other_func() } ) } tester_func_with()