testthat: expect_output – R documentation

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expect_output

Does code print output to the console?

Description

Test for output produced by print() or cat(). This is best used for very simple output; for more complex cases use verify_output().

Usage

expect_output(
  object,
  regexp = NULL,
  ...,
  info = NULL,
  label = NULL,
  width = 80
)

Arguments

`object`	Object to test. Supports limited unquoting to make it easier to generate readable failures within a function or for loop. See quasi_label for more details.
`regexp`	Regular expression to test against. A character vector giving a regular expression that must match the output. If `NULL`, the default, asserts that there should output, but doesn't check for a specific value. If `NA`, asserts that there should be no output.
`...`	Arguments passed on to `expect_match` `all` Should all elements of actual value match `regexp` (TRUE), or does only one need to match (FALSE) `perl` logical. Should Perl-compatible regexps be used? `fixed` logical. If `TRUE`, `pattern` is a string to be matched as is. Overrides all conflicting arguments.
`info`	Extra information to be included in the message. This argument is soft-deprecated and should not be used in new code. Instead see alternatives in quasi_label.
`label`	Used to customise failure messages. For expert use only.
`width`	Number of characters per line of output. This does not inherit from `getOption("width")` so that tests always use the same output width, minimising spurious differences.

Value

The first argument, invisibly.

Examples

str(mtcars)
expect_output(str(mtcars), "32 obs")
expect_output(str(mtcars), "11 variables")

# You can use the arguments of grepl to control the matching
expect_output(str(mtcars), "11 VARIABLES", ignore.case = TRUE)
expect_output(str(mtcars), "$ mpg", fixed = TRUE)

testthat

Unit Testing for R

v3.0.2

MIT + file LICENSE

Authors

Hadley Wickham [aut, cre], RStudio [cph, fnd], R Core team [ctb] (Implementation of utils::recover())

Initial release