diff --git a/src/modules/quest/quest.service.test.ts b/src/modules/quest/quest.service.test.ts
new file mode 100644
index 0000000..6460382
--- /dev/null
+++ b/src/modules/quest/quest.service.test.ts
@@ -0,0 +1,154 @@
+import { describe, it, expect, mock, beforeEach } from "bun:test";
+import { questService } from "./quest.service";
+import { userQuests } from "@/db/schema";
+import { eq, and } from "drizzle-orm";
+
+// Mock dependencies
+const mockFindFirst = mock();
+const mockFindMany = mock();
+const mockInsert = mock();
+const mockUpdate = mock();
+const mockDelete = mock();
+const mockValues = mock();
+const mockReturning = mock();
+const mockSet = mock();
+const mockWhere = mock();
+const mockOnConflictDoNothing = mock();
+
+// Chain setup
+mockInsert.mockReturnValue({ values: mockValues });
+mockValues.mockReturnValue({
+    onConflictDoNothing: mockOnConflictDoNothing
+});
+mockOnConflictDoNothing.mockReturnValue({ returning: mockReturning });
+
+mockUpdate.mockReturnValue({ set: mockSet });
+mockSet.mockReturnValue({ where: mockWhere });
+mockWhere.mockReturnValue({ returning: mockReturning });
+
+// Mock DrizzleClient
+mock.module("@/lib/DrizzleClient", () => {
+    const createMockTx = () => ({
+        query: {
+            userQuests: { findFirst: mockFindFirst, findMany: mockFindMany },
+        },
+        insert: mockInsert,
+        update: mockUpdate,
+        delete: mockDelete,
+    });
+
+    return {
+        DrizzleClient: {
+            ...createMockTx(),
+            transaction: async (cb: any) => cb(createMockTx()),
+        }
+    };
+});
+
+// Mock External Services
+const mockModifyUserBalance = mock();
+mock.module("@/modules/economy/economy.service", () => ({
+    economyService: {
+        modifyUserBalance: mockModifyUserBalance
+    }
+}));
+
+const mockAddXp = mock();
+mock.module("@/modules/leveling/leveling.service", () => ({
+    levelingService: {
+        addXp: mockAddXp
+    }
+}));
+
+describe("questService", () => {
+    beforeEach(() => {
+        mockFindFirst.mockReset();
+        mockFindMany.mockReset();
+        mockInsert.mockClear();
+        mockUpdate.mockClear();
+        mockValues.mockClear();
+        mockReturning.mockClear();
+        mockSet.mockClear();
+        mockWhere.mockClear();
+        mockOnConflictDoNothing.mockClear();
+        mockModifyUserBalance.mockClear();
+        mockAddXp.mockClear();
+    });
+
+    describe("assignQuest", () => {
+        it("should assign quest", async () => {
+            mockReturning.mockResolvedValue([{ userId: 1n, questId: 101 }]);
+
+            const result = await questService.assignQuest("1", 101);
+
+            expect(result).toEqual([{ userId: 1n, questId: 101 }] as any);
+            expect(mockInsert).toHaveBeenCalledWith(userQuests);
+            expect(mockValues).toHaveBeenCalledWith({
+                userId: 1n,
+                questId: 101,
+                progress: 0
+            });
+        });
+    });
+
+    describe("updateProgress", () => {
+        it("should update progress", async () => {
+            mockReturning.mockResolvedValue([{ userId: 1n, questId: 101, progress: 50 }]);
+
+            const result = await questService.updateProgress("1", 101, 50);
+
+            expect(result).toEqual([{ userId: 1n, questId: 101, progress: 50 }] as any);
+            expect(mockUpdate).toHaveBeenCalledWith(userQuests);
+            expect(mockSet).toHaveBeenCalledWith({ progress: 50 });
+        });
+    });
+
+    describe("completeQuest", () => {
+        it("should complete quest and grant rewards", async () => {
+            const mockUserQuest = {
+                userId: 1n,
+                questId: 101,
+                completedAt: null,
+                quest: {
+                    rewards: { balance: 100, xp: 50 }
+                }
+            };
+            mockFindFirst.mockResolvedValue(mockUserQuest);
+
+            const result = await questService.completeQuest("1", 101);
+
+            expect(result.success).toBe(true);
+            expect(result.rewards.balance).toBe(100n);
+            expect(result.rewards.xp).toBe(50n);
+
+            // Check updates
+            expect(mockUpdate).toHaveBeenCalledWith(userQuests);
+            expect(mockSet).toHaveBeenCalledWith({ completedAt: expect.any(Date) });
+
+            // Check service calls
+            expect(mockModifyUserBalance).toHaveBeenCalledWith("1", 100n, 'QUEST_REWARD', expect.any(String), null, expect.anything());
+            expect(mockAddXp).toHaveBeenCalledWith("1", 50n, expect.anything());
+        });
+
+        it("should throw if quest not assigned", async () => {
+            mockFindFirst.mockResolvedValue(null);
+            expect(questService.completeQuest("1", 101)).rejects.toThrow("Quest not assigned");
+        });
+
+        it("should throw if already completed", async () => {
+            mockFindFirst.mockResolvedValue({ completedAt: new Date() });
+            expect(questService.completeQuest("1", 101)).rejects.toThrow("Quest already completed");
+        });
+    });
+
+    describe("getUserQuests", () => {
+        it("should return user quests", async () => {
+            const mockData = [{ questId: 1 }, { questId: 2 }];
+            mockFindMany.mockResolvedValue(mockData);
+
+            const result = await questService.getUserQuests("1");
+
+            expect(result).toEqual(mockData as any);
+        });
+    });
+});