util: test improvements

src/util.rs

@@ -17,10 +17,95 @@ pub const fn index(width: usize, height: usize, x: f32, y: f32) -> usize {
 mod test {
     use super::*;
 
-    #[test]
-    fn wrap_test() {
-        assert_eq!(wrap(1.1, 1.0), 0.100000024); // floating point weirdness
-        assert_eq!(wrap(0.5, 1.0), 0.5);
-        assert_eq!(wrap(-1.0, 2.0), 1.0);
+    mod wrap {
+        use super::*;
+        #[test]
+        fn over() {
+            assert_eq!(wrap(1.1, 1.0), 0.100000024); // floating point weirdness
+        }
+
+        #[test]
+        fn middle() {
+            assert_eq!(wrap(0.5, 1.0), 0.5);
+        }
+
+        #[test]
+        fn under() {
+            assert_eq!(wrap(-1.0, 2.0), 1.0);
+        }
+    }
+
+    mod index {
+        use super::*;
+
+        #[test]
+        fn basic_positive_coordinates() {
+            let width = 4;
+            let height = 4;
+            assert_eq!(index(width, height, 1.5, 2.5), 9);
+        }
+
+        #[test]
+        fn negative_x_coordinate() {
+            let width = 8;
+            let height = 8;
+            assert_eq!(index(width, height, -3.2, 5.6), 44);
+        }
+
+        #[test]
+        fn exact_boundary_values() {
+            let width = 16;
+            let height = 16;
+            assert_eq!(index(width, height, 16.0, 0.0), 0);
+        }
+
+        #[test]
+        fn large_coordinates() {
+            let width = 2;
+            let height = 2;
+            assert_eq!(index(width, height, 1000.0, 2000.0), 0);
+        }
+
+        #[test]
+        fn negative_x_and_y() {
+            let width = 4;
+            let height = 4;
+            assert_eq!(index(width, height, -1.5, -0.5), 14);
+        }
+
+        #[test]
+        fn fractional_truncation() {
+            let width = 4;
+            let height = 4;
+            assert_eq!(index(width, height, 3.9, 3.999), 15);
+        }
+
+        #[test]
+        fn zero_coordinates() {
+            let width = 4;
+            let height = 4;
+            assert_eq!(index(width, height, 0.0, 0.0), 0);
+        }
+
+        #[test]
+        fn x_equals_width() {
+            let width = 8;
+            let height = 8;
+            assert_eq!(index(width, height, 8.0, 0.0), 0);
+        }
+
+        #[test]
+        fn y_negative_beyond_height() {
+            let width = 4;
+            let height = 4;
+            assert_eq!(index(width, height, 0.0, -4.5), 0);
+        }
+
+        #[test]
+        fn width_and_height_one() {
+            let width = 1;
+            let height = 1;
+            assert_eq!(index(width, height, 123.4, -56.7), 0);
+        }
     }
 }