R: Expectation: does code print output to the console?

expect_output {testthat} | R Documentation

## Expectation: 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.

### See Also

Other expectations: `comparison-expectations`, `equality-expectations`, `expect_error()`, `expect_length()`, `expect_match()`, `expect_message()`, `expect_named()`, `expect_null()`, `expect_silent()`, `inheritance-expectations`, `logical-expectations`

### 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)

[Package testthat version 2.3.2 Index]