Add assertions and tests for freedom unit converter

R/convert_to_freedom_units.R

@@ -16,6 +16,17 @@
 #' convert_to_freedom_units(grades = c(1.3, 2.8))
 #'
 convert_to_freedom_units <- function(grades, max_passing_grade = 4, min_passing_grade = 1) {
+
+  if (max_passing_grade != 4 || min_passing_grade != 1) {
+    warning("The maximum passing grade and the minimum passing grade should almost always be 4 and 1, respectively, in the US grading system. Are you sure this should be changed?")
+  }
+
+  assertthat::assert_that(
+    grades >= 1.0,
+    grades <= 5.0,
+    msg = "grades must be between 1.0 and 5.0 for the Bavarian formula to work."
+  )
+
   # Convert grades to freedom units
   freedom_units <- 1 + ((max_passing_grade - grades) / (max_passing_grade - min_passing_grade)) * 3
 

tests/testthat/test-convert_to_freedom_units.R

@@ -16,3 +16,12 @@ test_that("conversion from German to custom US functions", {
   expect_vector(convert_to_freedom_units(1:5, max_passing_grade = 4, min_passing_grade = 2))
   expect_length(convert_to_freedom_units(1:5, max_passing_grade = 4, min_passing_grade = 2), 5)
 })
+
+test_that("check function assertions", {
+  expect_error(convert_to_freedom_units(0), "grades must be between 1.0 and 5.0 for the Bavarian formula to work.")
+  expect_error(convert_to_freedom_units(6), "grades must be between 1.0 and 5.0 for the Bavarian formula to work.")
+})
+
+test_that("check warning", {
+  expect_warning(convert_to_freedom_units(1:5, max_passing_grade = 3, min_passing_grade = 2), "The maximum passing grade and the minimum passing grade should almost always be 4 and 1, respectively, in the US grading system. Are you sure this should be changed?")
+})