1 files changed, 166 insertions, 0 deletions
diff --git a/apps/web/src/rendering/__tests__/transition.test.ts b/apps/web/src/rendering/__tests__/transition.test.ts
new file mode 100644
index 00000000..4421fe58
--- /dev/null
+++ b/apps/web/src/rendering/__tests__/transition.test.ts
@@ -0,0 +1,166 @@
+import { describe, expect, test } from "bun:test";
+import {
+	applyVisualTransition,
+	buildTransitionFromParams,
+} from "@/rendering/transition";
+import type { Transform } from "@/rendering";
+import { TICKS_PER_SECOND } from "@/wasm";
+
+const baseTransform: Transform = {
+	scaleX: 1,
+	scaleY: 1,
+	position: { x: 0, y: 0 },
+	rotate: 0,
+};
+
+describe("visual transitions", () => {
+	test("fade ramps opacity at clip edges", () => {
+		const transition = buildTransitionFromParams({
+			params: {
+				"transition.kind": "fade",
+				"transition.inDuration": 1,
+				"transition.outDuration": 1,
+			},
+		});
+
+		expect(
+			applyVisualTransition({
+				baseTransform,
+				transition,
+				localTime: 0,
+				duration: 4 * TICKS_PER_SECOND,
+				canvasWidth: 100,
+			}).opacityMultiplier,
+		).toBe(0);
+		expect(
+			applyVisualTransition({
+				baseTransform,
+				transition,
+				localTime: 2 * TICKS_PER_SECOND,
+				duration: 4 * TICKS_PER_SECOND,
+				canvasWidth: 100,
+			}).opacityMultiplier,
+		).toBe(1);
+		expect(
+			applyVisualTransition({
+				baseTransform,
+				transition,
+				localTime: 4 * TICKS_PER_SECOND,
+				duration: 4 * TICKS_PER_SECOND,
+				canvasWidth: 100,
+			}).opacityMultiplier,
+		).toBe(0);
+	});
+
+	test("slide left moves in and out across canvas", () => {
+		const transition = buildTransitionFromParams({
+			params: {
+				"transition.kind": "push-left",
+				"transition.inDuration": 1,
+				"transition.outDuration": 1,
+			},
+		});
+
+		const enter = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 0,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+		const middle = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 2 * TICKS_PER_SECOND,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+		const leave = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 4 * TICKS_PER_SECOND,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+
+		expect(enter.transform.position.x).toBe(100);
+		expect(middle.transform.position.x).toBe(0);
+		expect(leave.transform.position.x).toBe(-100);
+		expect(leave.opacityMultiplier).toBe(1);
+	});
+
+	test("slide right mirrors horizontal entry and exit", () => {
+		const transition = buildTransitionFromParams({
+			params: {
+				"transition.kind": "push-right",
+				"transition.inDuration": 1,
+				"transition.outDuration": 1,
+			},
+		});
+
+		const enter = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 0,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+		const middle = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 2 * TICKS_PER_SECOND,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+		const leave = applyVisualTransition({
+			baseTransform,
+			transition,
+			localTime: 4 * TICKS_PER_SECOND,
+			duration: 4 * TICKS_PER_SECOND,
+			canvasWidth: 100,
+		});
+
+		expect(enter.transform.position.x).toBe(-100);
+		expect(middle.transform.position.x).toBe(0);
+		expect(leave.transform.position.x).toBe(100);
+		expect(enter.opacityMultiplier).toBe(1);
+	});
+
+	test("zoom and spin variants converge on the base transform", () => {
+		const applyKind = ({
+			kind,
+			localTime,
+		}: {
+			kind: "zoom" | "zoom-out" | "spin";
+			localTime: number;
+		}) =>
+			applyVisualTransition({
+				baseTransform,
+				transition: buildTransitionFromParams({
+					params: {
+						"transition.kind": kind,
+						"transition.inDuration": 1,
+						"transition.outDuration": 0,
+					},
+				}),
+				localTime,
+				duration: 4 * TICKS_PER_SECOND,
+				canvasWidth: 100,
+			});
+
+		expect(applyKind({ kind: "zoom", localTime: 0 }).transform.scaleX).toBe(
+			0.96,
+		);
+		expect(applyKind({ kind: "zoom-out", localTime: 0 }).transform.scaleX).toBe(
+			1.04,
+		);
+		expect(applyKind({ kind: "spin", localTime: 0 }).transform.rotate).toBe(-6);
+
+		const settledSpin = applyKind({
+			kind: "spin",
+			localTime: 2 * TICKS_PER_SECOND,
+		});
+		expect(settledSpin.transform.scaleX).toBe(1);
+		expect(settledSpin.transform.rotate).toBe(0);
+	});
+});