Does code return a visible or invisible object?

Source: R/expect-invisible.R

Use this to test whether a function returns a visible or invisible output. Typically you'll use this to check that functions called primarily for their side-effects return their data argument invisibly.

expect_invisible(call, label = NULL)

expect_visible(call, label = NULL)

Arguments

call

A function call.
label

Used to customise failure messages. For expert use only.

Value

The evaluated call, invisibly.

Examples

expect_invisible(x <- 10)
expect_visible(x)

# Typically you'll assign the result of the expectation so you can
# also check that the value is as you expect.
greet <- function(name) {
  message("Hi ", name)
  invisible(name)
}
out <- expect_invisible(greet("Hadley"))

#> Hi Hadley
expect_equal(out, "Hadley")