
library(testthat)

source("user_code.R")
test_that("add_three adds 3 to input", {
    expect_true(exists("add_three"), info = "The add_three function does not exist.")
    expect_true(is.function(add_three), info = "add_three is not a function.")
    expect_equal(add_three(4), 7, info = "add_three(4) should return 7.")
    expect_equal(add_three(-2), 1, info = "add_three(-2) should return 1.")
})

test_that("is_even returns TRUE for even numbers and FALSE for odd numbers", {
    expect_true(exists("is_even"), info = "The is_even function does not exist.")
    expect_true(is.function(is_even), info = "is_even is not a function.")
    expect_true(is_even(2), info = "is_even(2) should return TRUE.")
    expect_true(is_even(0), info = "is_even(0) should return TRUE.")
    expect_false(is_even(3), info = "is_even(3) should return FALSE.")
    expect_false(is_even(-1), info = "is_even(-1) should return FALSE.")
})

test_that("concat_strings concatenates two strings without separator", {
    expect_true(exists("concat_strings"), info = "The concat_strings function does not exist.")
    expect_true(is.function(concat_strings), info = "concat_strings is not a function.")
    expect_equal(concat_strings("Hello", "World"), "HelloWorld", info = "concat_strings('Hello', 'World') should return 'HelloWorld'.")
    expect_equal(concat_strings("a", "b"), "ab", info = "concat_strings('a', 'b') should return 'ab'.")
    expect_equal(concat_strings("", "test"), "test", info = "concat_strings('', 'test') should return 'test'.")
})

test_main.R

Master the art of writing and using functions in R, from basic syntax to advanced functional programming techniques. This course guides you through creating your own functions, leveraging anonymous functions, and applying functional programming concepts to solve real-world problems in R.

Learn how to define, call, and utilize functions in R, including understanding parameters, return values, and default arguments.

Discover how to use anonymous (inline) functions for concise, on-the-fly operations, and see how they fit into R's functional programming paradigm.

Apply functional programming concepts in R to solve real-world problems, focusing on writing concise, reusable, and efficient code.

Challenge: Create an Anonymous Function

Solution