3 The basics of saying hello

Let’s define a function for our R package:

#' Say hello to someone
#' 
#' @param name Name of a person
#' @param exclamation Whether to include an exclamation mark
#' @export 
say_hello <- function(name, exclamation = TRUE) {
  paste0("Hello ", name, ifelse(exclamation, "!", "."))
}

Code chunks whose first line starts with #' are added to the package.

We can try running it.

say_hello("Jacob")

## [1] "Hello Jacob!"

That code chunk does not start with #', so it is not added to the package.

Let’s write some tests to make sure the function behaves as desired:

testthat::test_that("say_hello works", {
  testthat::expect_equal(say_hello("Jacob"), "Hello Jacob!")
  testthat::expect_equal(say_hello("Jacob", exclamation = FALSE), "Hello Jacob.")
})

## Test passed 🥇

Code chunks that have one or more lines starting with test_that( (or testthat::test_that() are added to the package as tests.