2 files changed, 92 insertions, 0 deletions
diff --git a/apps/web/src/retime/__tests__/resolve.test.ts b/apps/web/src/retime/__tests__/resolve.test.ts
new file mode 100644
index 00000000..bb7b9a6d
--- /dev/null
+++ b/apps/web/src/retime/__tests__/resolve.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, test } from "bun:test";
+import {
+	getClipTimeAtSourceTime,
+	getEffectiveRateAt,
+	getSourceTimeAtClipTime,
+	getTimelineDurationForSourceSpan,
+} from "@/retime";
+import type { RetimeConfig } from "@/timeline";
+
+const twoX: RetimeConfig = { rate: 2 };
+const halfX: RetimeConfig = { rate: 0.5 };
+
+describe("retime resolve", () => {
+	test("maps clip time to source time at 2x speed", () => {
+		expect(getSourceTimeAtClipTime({ clipTime: 5, retime: twoX })).toBe(10);
+	});
+
+	test("maps clip time to source time at 0.5x speed", () => {
+		expect(getSourceTimeAtClipTime({ clipTime: 4, retime: halfX })).toBe(2);
+	});
+
+	test("returns clip time unchanged when no retime", () => {
+		expect(getSourceTimeAtClipTime({ clipTime: 7 })).toBe(7);
+	});
+
+	test("inverts source time back to clip time at 2x speed", () => {
+		expect(getClipTimeAtSourceTime({ sourceTime: 10, retime: twoX })).toBe(5);
+	});
+
+	test("returns effective rate", () => {
+		expect(getEffectiveRateAt({ retime: twoX })).toBe(2);
+		expect(getEffectiveRateAt({})).toBe(1);
+	});
+
+	test("derives timeline duration for a visible source span", () => {
+		expect(
+			getTimelineDurationForSourceSpan({ sourceSpan: 10, retime: twoX }),
+		).toBe(5);
+		expect(
+			getTimelineDurationForSourceSpan({ sourceSpan: 10, retime: halfX }),
+		).toBe(20);
+	});
+
+	test("clamps invalid rates to 1", () => {
+		expect(getSourceTimeAtClipTime({ clipTime: 5, retime: { rate: 0 } })).toBe(
+			5,
+		);
+		expect(
+			getSourceTimeAtClipTime({ clipTime: 5, retime: { rate: -1 } }),
+		).toBe(5);
+	});
+
+	test("caps retime rates above 5x", () => {
+		expect(getSourceTimeAtClipTime({ clipTime: 5, retime: { rate: 100 } })).toBe(
+			25,
+		);
+		expect(
+			getTimelineDurationForSourceSpan({ sourceSpan: 10, retime: { rate: 100 } }),
+		).toBe(2);
+	});
+});
diff --git a/apps/web/src/retime/__tests__/split.test.ts b/apps/web/src/retime/__tests__/split.test.ts
new file mode 100644
index 00000000..3c7bef63
--- /dev/null
+++ b/apps/web/src/retime/__tests__/split.test.ts
@@ -0,0 +1,31 @@
+import { describe, expect, test } from "bun:test";
+import {
+	getSourceSpanAtClipTime,
+	splitRetimeAtClipTime,
+} from "@/retime";
+import type { RetimeConfig } from "@/timeline";
+
+describe("retime split", () => {
+	test("measures source span at a clip time", () => {
+		const retime: RetimeConfig = { rate: 2 };
+		expect(getSourceSpanAtClipTime({ clipTime: 5, retime })).toBe(10);
+	});
+
+	test("returns zero for non-positive clip time", () => {
+		expect(getSourceSpanAtClipTime({ clipTime: 0 })).toBe(0);
+		expect(getSourceSpanAtClipTime({ clipTime: -1 })).toBe(0);
+	});
+
+	test("passes the same retime to both halves when splitting", () => {
+		const retime: RetimeConfig = { rate: 1.5 };
+		const result = splitRetimeAtClipTime({ retime, splitClipTime: 3 });
+		expect(result.left).toBe(retime);
+		expect(result.right).toBe(retime);
+	});
+
+	test("returns undefined on both sides when no retime", () => {
+		const result = splitRetimeAtClipTime({ splitClipTime: 3 });
+		expect(result.left).toBeUndefined();
+		expect(result.right).toBeUndefined();
+	});
+});