
library(testthat)

source("user_code.R")
test_that("returns only passed students", {
  students_df <- data.frame(
    name = c("Alice", "Bob", "Charlie", "David", "Eva"),
    score = c(85, 58, 92, 73, 66),
    passed = c(TRUE, FALSE, TRUE, TRUE, FALSE)
  )
  result <- filter_and_sort_passed_students(students_df)
  expect_true(all(result$passed == TRUE),
    info = "Result should only contain students who passed.")
  expect_equal(nrow(result), 3,
    info = "Result should have 3 rows for passed students.")
})

test_that("sorts by score descending", {
  students_df <- data.frame(
    name = c("Alice", "Bob", "Charlie", "David", "Eva"),
    score = c(85, 58, 92, 73, 66),
    passed = c(TRUE, FALSE, TRUE, TRUE, FALSE)
  )
  result <- filter_and_sort_passed_students(students_df)
  expect_equal(result$score, sort(result$score, decreasing = TRUE),
    info = "Scores should be sorted in descending order.")
})

test_that("preserves all columns", {
  students_df <- data.frame(
    name = c("Alice", "Bob", "Charlie", "David", "Eva"),
    score = c(85, 58, 92, 73, 66),
    passed = c(TRUE, FALSE, TRUE, TRUE, FALSE)
  )
  result <- filter_and_sort_passed_students(students_df)
  expect_equal(names(result), names(students_df),
    info = "All columns should be preserved.")
})

test_that("returns empty data frame if no students passed", {
  students_df <- data.frame(
    name = c("Alice", "Bob"),
    score = c(10, 20),
    passed = c(FALSE, FALSE)
  )
  result <- filter_and_sort_passed_students(students_df)
  expect_equal(nrow(result), 0,
    info = "Should return 0 rows if no students passed.")
  expect_equal(names(result), names(students_df),
    info = "Column names should match input data frame.")
})

test_main.R

Focus on practical skills for cleaning and transforming tabular data in R using data frames. Learn to create, modify, filter, and sort data for analysis, with hands-on challenges to reinforce each concept.

Challenge: Filter and Sort Data

Solution

Challenge: Filter and Sort Data

Solution