1 files changed, 65 insertions, 0 deletions
diff --git a/apps/web/src/timeline/__tests__/audio-state.test.ts b/apps/web/src/timeline/__tests__/audio-state.test.ts
new file mode 100644
index 00000000..91c422cb
--- /dev/null
+++ b/apps/web/src/timeline/__tests__/audio-state.test.ts
@@ -0,0 +1,65 @@
+import { describe, expect, test } from "bun:test";
+import {
+	dBToLinear,
+	getTrackVolume,
+	resolveEffectiveAudioGain,
+} from "@/timeline/audio-state";
+import type { AudioElement, AudioTrack } from "@/timeline";
+import { ZERO_MEDIA_TIME } from "@/wasm";
+
+function audioElement(params?: AudioElement["params"]): AudioElement {
+	return {
+		id: "audio-1",
+		name: "Audio",
+		type: "audio",
+		sourceType: "upload",
+		mediaId: "media-1",
+		duration: ZERO_MEDIA_TIME,
+		startTime: ZERO_MEDIA_TIME,
+		trimStart: ZERO_MEDIA_TIME,
+		trimEnd: ZERO_MEDIA_TIME,
+		params: params ?? { volume: 0, muted: false },
+	};
+}
+
+describe("audio state", () => {
+	test("track volume offsets element gain in decibels", () => {
+		const gain = resolveEffectiveAudioGain({
+			element: audioElement({ volume: -6, muted: false }),
+			trackVolume: -6,
+			localTime: 0,
+		});
+
+		expect(gain).toBeCloseTo(dBToLinear(-12), 6);
+	});
+	test("track volume and mute resolve to playback gain", () => {
+		const element = audioElement({ volume: 0, muted: false });
+
+		expect(
+			resolveEffectiveAudioGain({ element, trackVolume: 0, localTime: 0 }),
+		).toBe(1);
+		expect(
+			resolveEffectiveAudioGain({ element, trackVolume: -6, localTime: 0 }),
+		).toBeCloseTo(dBToLinear(-6), 6);
+		expect(
+			resolveEffectiveAudioGain({
+				element,
+				trackMuted: true,
+				trackVolume: 0,
+				localTime: 0,
+			}),
+		).toBe(0);
+	});
+
+	test("missing track volume defaults to unity", () => {
+		const track: AudioTrack = {
+			id: "track-1",
+			name: "Audio track",
+			type: "audio",
+			elements: [],
+			muted: false,
+		};
+
+		expect(getTrackVolume({ track })).toBe(0);
+	});
+});