diff --git a/src/modules/class/class.service.test.ts b/src/modules/class/class.service.test.ts
new file mode 100644
index 0000000..4e0e591
--- /dev/null
+++ b/src/modules/class/class.service.test.ts
@@ -0,0 +1,209 @@
+import { describe, it, expect, mock, beforeEach } from "bun:test";
+import { classService } from "./class.service";
+import { classes, users } from "@/db/schema";
+import { eq, sql } from "drizzle-orm";
+
+// Define mock functions
+const mockFindMany = mock();
+const mockFindFirst = mock();
+const mockInsert = mock();
+const mockUpdate = mock();
+const mockDelete = mock();
+const mockValues = mock();
+const mockReturning = mock();
+const mockSet = mock();
+const mockWhere = mock();
+
+// Chainable mock setup
+mockInsert.mockReturnValue({ values: mockValues });
+mockValues.mockReturnValue({ returning: mockReturning });
+
+mockUpdate.mockReturnValue({ set: mockSet });
+mockSet.mockReturnValue({ where: mockWhere });
+mockWhere.mockReturnValue({ returning: mockReturning });
+
+mockDelete.mockReturnValue({ where: mockWhere }); // Fix for delete chaining if needed, usually delete(table).where(...)
+
+// Mock DrizzleClient
+mock.module("@/lib/DrizzleClient", () => {
+    return {
+        DrizzleClient: {
+            query: {
+                classes: {
+                    findMany: mockFindMany,
+                    findFirst: mockFindFirst,
+                },
+            },
+            insert: mockInsert,
+            update: mockUpdate,
+            delete: mockDelete,
+            transaction: async (cb: any) => {
+                return cb({
+                    query: {
+                        classes: {
+                            findMany: mockFindMany,
+                            findFirst: mockFindFirst,
+                        },
+                    },
+                    insert: mockInsert,
+                    update: mockUpdate,
+                    delete: mockDelete,
+                });
+            }
+        },
+    };
+});
+
+describe("classService", () => {
+    beforeEach(() => {
+        mockFindMany.mockReset();
+        mockFindFirst.mockReset();
+        mockInsert.mockClear();
+        mockUpdate.mockClear();
+        mockDelete.mockClear();
+        mockValues.mockClear();
+        mockReturning.mockClear();
+        mockSet.mockClear();
+        mockWhere.mockClear();
+    });
+
+    describe("getAllClasses", () => {
+        it("should return all classes", async () => {
+            const mockClasses = [{ id: 1n, name: "Warrior" }, { id: 2n, name: "Mage" }];
+            mockFindMany.mockResolvedValue(mockClasses);
+
+            const result = await classService.getAllClasses();
+
+            expect(result).toEqual(mockClasses as any);
+            expect(mockFindMany).toHaveBeenCalledTimes(1);
+        });
+    });
+
+    describe("assignClass", () => {
+        it("should assign class to user if class exists", async () => {
+            const mockClass = { id: 1n, name: "Warrior" };
+            const mockUser = { id: 123n, classId: 1n };
+
+            mockFindFirst.mockResolvedValue(mockClass);
+            mockReturning.mockResolvedValue([mockUser]);
+
+            const result = await classService.assignClass("123", 1n);
+
+            expect(result).toEqual(mockUser as any);
+            // Verify class check
+            expect(mockFindFirst).toHaveBeenCalledTimes(1);
+            // Verify update
+            expect(mockUpdate).toHaveBeenCalledWith(users);
+            expect(mockSet).toHaveBeenCalledWith({ classId: 1n });
+        });
+
+        it("should throw error if class not found", async () => {
+            mockFindFirst.mockResolvedValue(undefined);
+
+            expect(classService.assignClass("123", 99n)).rejects.toThrow("Class not found");
+        });
+    });
+
+    describe("getClassBalance", () => {
+        it("should return class balance", async () => {
+            const mockClass = { id: 1n, balance: 100n };
+            mockFindFirst.mockResolvedValue(mockClass);
+
+            const result = await classService.getClassBalance(1n);
+
+            expect(result).toBe(100n);
+        });
+
+        it("should return 0n if class has no balance or not found", async () => {
+            mockFindFirst.mockResolvedValue(null);
+            const result = await classService.getClassBalance(1n);
+            expect(result).toBe(0n);
+
+            mockFindFirst.mockResolvedValue({ id: 1n, balance: null });
+            const result2 = await classService.getClassBalance(1n);
+            expect(result2).toBe(0n);
+        });
+    });
+
+    describe("modifyClassBalance", () => {
+        it("should modify class balance successfully", async () => {
+            const mockClass = { id: 1n, balance: 100n };
+            const updatedClass = { id: 1n, balance: 150n };
+
+            mockFindFirst.mockResolvedValue(mockClass);
+            mockReturning.mockResolvedValue([updatedClass]);
+
+            const result = await classService.modifyClassBalance(1n, 50n);
+
+            expect(result).toEqual(updatedClass as any);
+            expect(mockUpdate).toHaveBeenCalledWith(classes);
+            // Note: sql template literal matching might be tricky, checking strict call might fail if not exact object ref
+            // We verify at least mockSet was called
+            expect(mockSet).toHaveBeenCalled();
+        });
+
+        it("should throw if class not found", async () => {
+            mockFindFirst.mockResolvedValue(undefined);
+            expect(classService.modifyClassBalance(1n, 50n)).rejects.toThrow("Class not found");
+        });
+
+        it("should throw if insufficient funds", async () => {
+            const mockClass = { id: 1n, balance: 10n };
+            mockFindFirst.mockResolvedValue(mockClass);
+
+            expect(classService.modifyClassBalance(1n, -20n)).rejects.toThrow("Insufficient class funds");
+        });
+    });
+
+    describe("updateClass", () => {
+        it("should update class details", async () => {
+            const updateData = { name: "Super Warrior" };
+            const updatedClass = { id: 1n, name: "Super Warrior" };
+
+            mockReturning.mockResolvedValue([updatedClass]);
+
+            const result = await classService.updateClass(1n, updateData);
+
+            expect(result).toEqual(updatedClass as any);
+            expect(mockUpdate).toHaveBeenCalledWith(classes);
+            expect(mockSet).toHaveBeenCalledWith(updateData);
+        });
+    });
+
+    describe("createClass", () => {
+        it("should create a new class", async () => {
+            const newClassData = { name: "Archer", description: "Bow user" };
+            const createdClass = { id: 3n, ...newClassData };
+
+            mockReturning.mockResolvedValue([createdClass]);
+
+            const result = await classService.createClass(newClassData as any);
+
+            expect(result).toEqual(createdClass as any);
+            expect(mockInsert).toHaveBeenCalledWith(classes);
+            expect(mockValues).toHaveBeenCalledWith(newClassData);
+        });
+    });
+
+    describe("deleteClass", () => {
+        it("should delete a class", async () => {
+            mockDelete.mockReturnValue({ where: mockWhere });
+            // The chain is delete(table).where(...) for delete
+
+            // Wait, in user.service.test.ts:
+            // mockDelete called without chain setup in the file provided?
+            // "mockDelete = mock()"
+            // And in mock: "delete: mockDelete"
+            // And in usage: "await txFn.delete(users).where(...)"
+            // So mockDelete must return an object with where.
+
+            mockDelete.mockReturnValue({ where: mockWhere });
+
+            await classService.deleteClass(1n);
+
+            expect(mockDelete).toHaveBeenCalledWith(classes);
+            // We can't easily check 'where' arguments specifically without complex matcher if we don't return specific mock
+            expect(mockWhere).toHaveBeenCalled();
+        });
+    });
+});