expect-condition.md
In testthat: Unit Testing for R

regexp = NULL checks for presence of error

`null()` did not throw the expected error.

regexp = string matches for error message

"OK" did not throw the expected error.

check type of class and pattern

Code
  expect_error(stop("!"), regexp = 1)
Condition
  Error in `expect_error()`:
  ! `pattern` must be a single string, `NA`, or `NULL`, not the number 1.
Code
  expect_error(stop("!"), class = 1)
Condition
  Error in `expect_error()`:
  ! `class` must be a single string or `NULL`, not the number 1.

message method is called when expecting error

`fb()` threw an unexpected error.
Message: dispatched!
Class:   foobar/rlang_error/error/condition

condition class is included in failure

`f1()` did not throw a condition with class <bar>.

unused arguments generate an error

Code
  expect_condition(stop("Hi!"), foo = "bar")
Condition
  Error in `expect_condition()`:
  ! Can't specify `...` without `pattern`.
Code
  expect_condition(stop("Hi!"), "x", foo = "bar")
Condition
  Error in `expect_condition()`:
  ! Failed to compare condition to `pattern`.
  Caused by error in `grepl()`:
  ! unused argument (foo = "bar")