library(testthat)
source("user_code.R")

test_that("arrange_multiple_plots exists and is a function", {
  expect_true(exists("arrange_multiple_plots"), info = "arrange_multiple_plots function should exist.")
  expect_true(is.function(arrange_multiple_plots), info = "arrange_multiple_plots should be a function.")
  expect_error(arrange_multiple_plots(), NA, info = "arrange_multiple_plots should be callable without error.")
  png(tempfile())
  result <- arrange_multiple_plots()
  dev.off()
  #expect_true(is.null(result) || is.list(result), info = "arrange_multiple_plots should return NULL or invisible value.")
})

test_main.R

Master the foundational techniques of data visualization in R. This course guides you through the most important plotting tools and concepts, helping you create clear, insightful, and publication-ready graphics using base R and popular visualization approaches.

Explore the essential plotting tools and visualization strategies in R, focusing on practical skills for creating and customizing a wide range of charts and graphs.

Challenge: Arranging Multiple Plots

解答