diff --git a/src/app/api/dashboard/year/route.test.ts b/src/app/api/dashboard/year/route.test.ts
new file mode 100644
index 0000000..2c124a3
--- /dev/null
+++ b/src/app/api/dashboard/year/route.test.ts
@@ -0,0 +1,95 @@
+import { describe, expect, it, vi } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("next-auth", () => ({
+    getServerSession: vi.fn(),
+}));
+
+vi.mock("@/lib/auth", () => ({
+    authOptions: {},
+}));
+
+vi.mock("@/lib/githubViewer", () => ({
+    fetchViewerLogin: vi.fn(),
+}));
+
+vi.mock("@/lib/githubYearInReview", () => ({
+    fetchYearInReviewData: vi.fn(),
+}));
+
+describe("GET /api/dashboard/year", () => {
+    it("returns 401 if unauthorized", async () => {
+        const { getServerSession } = await import("next-auth");
+        vi.mocked(getServerSession).mockResolvedValueOnce(null);
+
+        const { GET } = await import("./route");
+        const req = new NextRequest("http://localhost/api/dashboard/year?year=2023");
+
+        const response = await GET(req);
+        expect(response.status).toBe(401);
+
+        const data = await response.json();
+        expect(data).toEqual({ error: "Unauthorized" });
+    });
+
+    it("returns 400 if year is invalid", async () => {
+        const { getServerSession } = await import("next-auth");
+        vi.mocked(getServerSession).mockResolvedValueOnce({
+            user: { login: "testuser" },
+            accessToken: "testtoken",
+            expires: "9999-12-31T23:59:59.999Z",
+        });
+
+        const { GET } = await import("./route");
+        const req = new NextRequest("http://localhost/api/dashboard/year?year=invalid");
+
+        const response = await GET(req);
+        expect(response.status).toBe(400);
+
+        const data = await response.json();
+        expect(data).toEqual({ error: "Invalid year" });
+    });
+
+    it("handles error path when fetching data fails", async () => {
+        const { getServerSession } = await import("next-auth");
+        vi.mocked(getServerSession).mockResolvedValueOnce({
+            user: { login: "testuser" },
+            accessToken: "testtoken",
+            expires: "9999-12-31T23:59:59.999Z",
+        });
+
+        const { fetchYearInReviewData } = await import("@/lib/githubYearInReview");
+        vi.mocked(fetchYearInReviewData).mockRejectedValueOnce(new Error("API Error"));
+
+        const { GET } = await import("./route");
+        const req = new NextRequest("http://localhost/api/dashboard/year?year=2023");
+
+        const response = await GET(req);
+        expect(response.status).toBe(500);
+
+        const data = await response.json();
+        expect(data).toEqual({ error: "API Error" });
+    });
+
+    it("returns 200 and data on success", async () => {
+        const { getServerSession } = await import("next-auth");
+        vi.mocked(getServerSession).mockResolvedValueOnce({
+            user: { login: "testuser" },
+            accessToken: "testtoken",
+            expires: "9999-12-31T23:59:59.999Z",
+        });
+
+        const { fetchYearInReviewData } = await import("@/lib/githubYearInReview");
+        const mockData = { totalContributions: 1000 };
+        vi.mocked(fetchYearInReviewData).mockResolvedValueOnce(mockData as unknown as Awaited<ReturnType<typeof fetchYearInReviewData>>);
+
+        const { GET } = await import("./route");
+        const req = new NextRequest("http://localhost/api/dashboard/year?year=2023");
+
+        const response = await GET(req);
+        expect(response.status).toBe(200);
+
+        const data = await response.json();
+        expect(data).toEqual(mockData);
+    });
+});