added test suite for count_classes function

tests/testthat/test-count_classes.R

@@ -1,3 +1,65 @@
-test_that("multiplication works", {
-  expect_equal(2 * 2, 4)
+# Function inputs for test cases ------------------------------------------
+
+set.seed(2024)
+
+two_classes_2_obs <- data.frame(class_labels = rep(c("class1",
+                                                       "class2"), 2),
+                                  values = round(runif(4), 1))
+two_classes_2_and_1_obs <- data.frame(class_labels = c(rep("class1", 2),
+                                                       "class2"),
+                                      values = round(runif(3), 1))
+one_class_2_obs <- data.frame(class_labels = c("class1", "class1"),
+                              values = round(runif(2), 1))
+empty_df  <- data.frame(class_labels = character(0),
+                        values = double(0))
+two_classes_two_obs_as_list <- list(class_labels = rep(c("class1",
+                                                         "class2"), 2),
+                                    values = round(runif(4), 1))
+
+
+# Expected function outputs for test cases --------------------------------
+
+two_classes_2_obs_output <- data.frame(class = c("class1", "class2"),
+                                         count = c(2,2))
+two_classes_2_and_1_obs_output <- data.frame(class = c("class1", "class2"),
+                                             count = c(2, 1))
+one_class_2_obs_output <- data.frame(class = "class1",
+                                     count = 2)
+empty_df_output <- data.frame(class = character(0),
+                              count = numeric(0))
+
+
+# Expected use test cases -------------------------------------------------
+
+test_that("`count_classes` should return a data frame, or tibble,
+with the number of rows corresponding to the number of unique classes
+in the `class_col` from the original dataframe. The new dataframe
+will have a `class column` whose values are the unique classes,
+and a `count` column, whose values will be the number of observations
+for each  class", {
+  expect_s3_class(count_classes(two_classes_2_obs, class_labels),
+                  "data.frame")
+  expect_equal(count_classes(two_classes_2_obs, class_labels),
+                    two_classes_2_obs_output, ignore_attr = TRUE)
+  expect_equal(count_classes(two_classes_2_and_1_obs, class_labels),
+                    two_classes_2_and_1_obs_output, ignore_attr = TRUE)
+})
+
+
+# Edge test cases ---------------------------------------------------------
+
+test_that("`count_classes` should return an empty data frame, or tibble,
+if the input to the function is an empty data frame", {
+  expect_equal(count_classes(one_class_2_obs, class_labels),
+                    one_class_2_obs_output, ignore_attr = TRUE)
+  expect_equal(count_classes(empty_df, class_labels),
+                    empty_df_output, ignore_attr = TRUE)
+})
+
+
+# Error test cases ---------------------------------------------------------
+
+test_that("`count_classes` should throw an error when incorrect types
+are passed to the `data_frame` argument", {
+  expect_error(count_classes(two_classes_two_obs_as_list, class_lables))
 })