expect_success: Test your custom expectations

In testthat: Unit Testing for R

Test your custom expectations

Description

expect_success() checks that there's exactly one success and no failures; expect_failure() checks that there's exactly one failure and no successes. expect_snapshot_failure() records the failure message so that you can manually check that it is informative.

Use show_failure() in examples to print the failure message without throwing an error.

Usage

expect_success(expr)

expect_failure(expr, message = NULL, ...)

expect_snapshot_failure(expr)

show_failure(expr)

Arguments

expr	Code to evaluate
message	Check that the failure message matches this regexp.
...	Other arguments passed on to expect_match().

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