1 files changed, 99 insertions, 0 deletions
diff --git a/apps/web/src/services/renderer/__tests__/scene-builder-transition.test.ts b/apps/web/src/services/renderer/__tests__/scene-builder-transition.test.ts
new file mode 100644
index 00000000..dd644f2a
--- /dev/null
+++ b/apps/web/src/services/renderer/__tests__/scene-builder-transition.test.ts
@@ -0,0 +1,99 @@
+import { describe, expect, test } from "bun:test";
+import { buildScene } from "@/services/renderer/scene-builder";
+import { ImageNode } from "@/services/renderer/nodes/image-node";
+import type { ImageElement, SceneTracks } from "@/timeline";
+import type { MediaAsset } from "@/media/types";
+import {
+	mediaTime,
+	type MediaTime,
+	TICKS_PER_SECOND,
+	ZERO_MEDIA_TIME,
+} from "@/wasm";
+
+function imageElement({
+	id,
+	mediaId,
+	startTime,
+	transitionDuration = 0,
+}: {
+	id: string;
+	mediaId: string;
+	startTime: MediaTime;
+	transitionDuration?: number;
+}): ImageElement {
+	return {
+		id,
+		name: id,
+		type: "image",
+		mediaId,
+		startTime,
+		duration: mediaTime({ ticks: 2 * TICKS_PER_SECOND }),
+		trimStart: ZERO_MEDIA_TIME,
+		trimEnd: ZERO_MEDIA_TIME,
+		params: {
+			"transform.positionX": 0,
+			"transform.positionY": 0,
+			"transform.scaleX": 1,
+			"transform.scaleY": 1,
+			"transform.rotate": 0,
+			opacity: 1,
+			blendMode: "normal",
+			"transition.kind": "fade",
+			"transition.inDuration": transitionDuration,
+			"transition.outDuration": 0,
+		},
+	};
+}
+
+function imageAsset(id: string): MediaAsset {
+	return {
+		id,
+		name: id,
+		type: "image",
+		file: new File([], `${id}.png`, { type: "image/png" }),
+		url: `blob:${id}`,
+	};
+}
+
+describe("scene transition boundaries", () => {
+	test("holds the outgoing slide through the incoming transition", () => {
+		const first = imageElement({
+			id: "first",
+			mediaId: "media-first",
+			startTime: ZERO_MEDIA_TIME,
+		});
+		const second = imageElement({
+			id: "second",
+			mediaId: "media-second",
+			startTime: mediaTime({ ticks: 3 * TICKS_PER_SECOND }),
+			transitionDuration: 1,
+		});
+		const tracks: SceneTracks = {
+			overlay: [],
+			main: {
+				id: "main",
+				name: "Main Track",
+				type: "video",
+				elements: [first, second],
+				muted: false,
+				hidden: false,
+			},
+			audio: [],
+		};
+		const scene = buildScene({
+			canvasSize: { width: 1920, height: 1080 },
+			tracks,
+			mediaAssets: [imageAsset("media-first"), imageAsset("media-second")],
+			duration: 5 * TICKS_PER_SECOND,
+			background: { type: "color", color: "transparent" },
+		});
+		const imageNodes = scene.children.filter(
+			(node): node is ImageNode => node instanceof ImageNode,
+		);
+
+		expect(imageNodes).toHaveLength(2);
+		expect(imageNodes[0].params.contentDuration).toBe(2 * TICKS_PER_SECOND);
+		expect(imageNodes[0].params.duration).toBe(4 * TICKS_PER_SECOND);
+		expect(imageNodes[1].params.transition?.inDuration).toBe(TICKS_PER_SECOND);
+	});
+});