diff --git a/src/lib/__tests__/github/handleRateLimit.test.ts b/src/lib/__tests__/github/handleRateLimit.test.ts
new file mode 100644
index 00000000..6114d0ee
--- /dev/null
+++ b/src/lib/__tests__/github/handleRateLimit.test.ts
@@ -0,0 +1,69 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { handleRateLimit } from "@/lib/github";
+import { RateLimitError } from "@/lib/types";
+
+describe("handleRateLimit", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2024-01-01T00:00:00Z"));
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("throws RateLimitError using X-RateLimit-Reset header when available", () => {
+    const timestamp = 1704069000; // 2024-01-01T00:30:00Z
+    const headers = new Headers();
+    headers.set("X-RateLimit-Reset", timestamp.toString());
+    const mockResponse = {
+      headers
+    } as unknown as Response;
+
+    expect(() => handleRateLimit(mockResponse)).toThrow(RateLimitError);
+    try {
+      handleRateLimit(mockResponse);
+    } catch (e) {
+      expect(e).toBeInstanceOf(RateLimitError);
+      const error = e as RateLimitError;
+      expect(error.resetAt.getTime()).toBe(timestamp * 1000);
+    }
+  });
+
+  it("throws RateLimitError using default time (1 hour from now) when header is missing", () => {
+    const headers = new Headers();
+    const mockResponse = {
+      headers
+    } as unknown as Response;
+
+    const expectedTimestamp = Math.floor(Date.now() / 1000) + 3600;
+
+    expect(() => handleRateLimit(mockResponse)).toThrow(RateLimitError);
+    try {
+      handleRateLimit(mockResponse);
+    } catch (e) {
+      expect(e).toBeInstanceOf(RateLimitError);
+      const error = e as RateLimitError;
+      expect(error.resetAt.getTime()).toBe(expectedTimestamp * 1000);
+    }
+  });
+
+  it("throws RateLimitError using default time when header is invalid", () => {
+    const headers = new Headers();
+    headers.set("X-RateLimit-Reset", "invalid");
+    const mockResponse = {
+      headers
+    } as unknown as Response;
+
+    const expectedTimestamp = Math.floor(Date.now() / 1000) + 3600;
+
+    expect(() => handleRateLimit(mockResponse)).toThrow(RateLimitError);
+    try {
+      handleRateLimit(mockResponse);
+    } catch (e) {
+      expect(e).toBeInstanceOf(RateLimitError);
+      const error = e as RateLimitError;
+      expect(error.resetAt.getTime()).toBe(expectedTimestamp * 1000);
+    }
+  });
+});