First round of animation improvements

test/animation/test_keyframe.c

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "dusktest.h"
+#include "animation/keyframe.h"
+
+static void test_keyframeGetValueInterpolatesLinear(void **state) {
+  keyframe_t keyframes[] = {
+    { .time = 0.0f, .value = 0.0f, .easing = EASING_LINEAR },
+    { .time = 1.0f, .value = 10.0f, .easing = EASING_LINEAR }
+  };
+
+  assert_float_equal(keyframeGetValue(keyframes, 2, 0.5f), 5.0f, 0.0001f);
+}
+
+static void test_keyframeGetValueClampsAtBoundaries(void **state) {
+  keyframe_t keyframes[] = {
+    { .time = 0.0f, .value = 0.0f, .easing = EASING_LINEAR },
+    { .time = 1.0f, .value = 10.0f, .easing = EASING_LINEAR }
+  };
+
+  // Exactly on, and beyond, the final keyframe: holds its value rather
+  // than dividing by zero (start == end at that boundary).
+  assert_float_equal(keyframeGetValue(keyframes, 2, 1.0f), 10.0f, 0.0001f);
+  assert_float_equal(keyframeGetValue(keyframes, 2, 5.0f), 10.0f, 0.0001f);
+
+  // Exactly on the first keyframe: same boundary case at the start.
+  assert_float_equal(keyframeGetValue(keyframes, 2, 0.0f), 0.0f, 0.0001f);
+}
+
+static void test_keyframeGetValueRespectsEasing(void **state) {
+  keyframe_t keyframes[] = {
+    { .time = 0.0f, .value = 0.0f, .easing = EASING_IN_QUAD },
+    { .time = 1.0f, .value = 10.0f, .easing = EASING_IN_QUAD }
+  };
+
+  // easingInQuad(0.5) = 0.25 -> lerp(0, 10, 0.25) = 2.5, not the linear
+  // midpoint (5.0).
+  assert_float_equal(keyframeGetValue(keyframes, 2, 0.5f), 2.5f, 0.0001f);
+}
+
+static void test_keyframeGetValueWithThreeKeyframes(void **state) {
+  keyframe_t keyframes[] = {
+    { .time = 0.0f, .value = 0.0f, .easing = EASING_LINEAR },
+    { .time = 1.0f, .value = 10.0f, .easing = EASING_LINEAR },
+    { .time = 2.0f, .value = 0.0f, .easing = EASING_LINEAR }
+  };
+
+  assert_float_equal(keyframeGetValue(keyframes, 3, 1.0f), 10.0f, 0.0001f);
+  assert_float_equal(keyframeGetValue(keyframes, 3, 1.5f), 5.0f, 0.0001f);
+}
+
+int main(int argc, char **argv) {
+  const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_keyframeGetValueInterpolatesLinear),
+    cmocka_unit_test(test_keyframeGetValueClampsAtBoundaries),
+    cmocka_unit_test(test_keyframeGetValueRespectsEasing),
+    cmocka_unit_test(test_keyframeGetValueWithThreeKeyframes),
+  };
+
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}