local_mocked_s3_method: Mock S3 and S4 methods

In testthat: Unit Testing for R

Mock S3 and S4 methods

Description

These functions allow you to temporarily override S3 and S4 methods that already exist. It works by using registerS3method()/setMethod() to temporarily replace the original definition.

Learn more about mocking in vignette("mocking").

Usage

local_mocked_s3_method(generic, signature, definition, frame = caller_env())

local_mocked_s4_method(generic, signature, definition, frame = caller_env())

Arguments

generic	A string giving the name of the generic.
signature	A character vector giving the signature of the method.
definition	A function providing the method definition.
frame	Calling frame which determines the scope of the mock. Only needed when wrapping in another local helper.

Examples

x <- as.POSIXlt(Sys.time())
local({
  local_mocked_s3_method("length", "POSIXlt", function(x) 42)
  length(x)
})

length(x)

testthat documentation built on Nov. 25, 2025, 5:09 p.m.