diff --git a/__tests__/exchangeRateService.test.ts b/__tests__/exchangeRateService.test.ts
new file mode 100644
index 0000000..c9c153c
--- /dev/null
+++ b/__tests__/exchangeRateService.test.ts
@@ -0,0 +1,94 @@
+import { describe, expect, it, jest, mock, beforeEach, beforeAll } from "bun:test";
+import { prepareExchangeRates, wipeExchangeRates } from '../src/content/exchangeRateService.ts'
+import { getStorageValue, setStorageValue } from '../src/content/storage'
+import { storage_exchangerates, storage_exchangerates_next, storage_exchangerates_update } from "../src/content/config";
+import { logDebug, logError } from '../src/content/utils/log';
+declare function GM_fetch(input: string | URL | globalThis.Request, init?: RequestInit): Promise<Response>
+
+// Mock the storage functions
+mock.module('../src/content/storage', () => ({
+  setStorageValue: mock(async (key: string, value: any) => {}),
+  getStorageValue: mock(async (key: string, defaultValue: any) => defaultValue)
+}));
+
+// Mock the log functions
+mock.module('../src/content/utils/log', () => ({
+  logDebug: mock(() => {}),
+  log: mock(() => {}),
+  logError: mock(() => {})
+}));
+
+describe('wipeExchangeRates', () => {
+  it('should clear exchange rate storage and set update timestamps', async () => {
+    await wipeExchangeRates();
+
+    expect(setStorageValue).toHaveBeenCalledWith(storage_exchangerates, null);
+    expect(setStorageValue).toHaveBeenCalledWith(storage_exchangerates_update, expect.any(String));
+    expect(setStorageValue).toHaveBeenCalledWith(storage_exchangerates_next, expect.any(String));
+    expect(logDebug).toHaveBeenCalled();
+  });
+});
+
+describe('prepareExchangeRates', () => {
+  const mockRates = { USD: 1, EUR: 0.85, GBP: 0.73 };
+
+  beforeAll(() => {
+    jest
+      .spyOn(global, 'GM_fetch')
+      .mockImplementation(() => {
+        return Promise.resolve({
+          ok: false,
+          status: 500
+        } as Response);
+      });
+  });
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should return stored rates if they are up to date', async () => {
+    (getStorageValue as jest.Mock).mockImplementation(async (key) => {
+      if (key === storage_exchangerates) return mockRates;
+      if (key === storage_exchangerates_update) return new Date().toISOString();
+      if (key === storage_exchangerates_next) return new Date(Date.now() + 100000).toISOString();
+      return null;
+    });
+
+    const rates = await prepareExchangeRates();
+    expect(rates).toEqual(mockRates);
+    expect(GM_fetch).not.toHaveBeenCalled();
+  });
+
+  it('should fetch new rates when they are expired', async () => {
+    (getStorageValue as jest.Mock).mockImplementation(async (key) => {
+      if (key === storage_exchangerates_update) return new Date(Date.now() - 100000).toISOString();
+      if (key === storage_exchangerates_next) return new Date(Date.now() - 50000).toISOString();
+      return null;
+    });
+    (GM_fetch as jest.Mock).mockResolvedValue({
+      ok: true,
+      json: async () => ({
+        rates: mockRates,
+        time_next_update_utc: new Date(Date.now() + 100000).toISOString()
+      })
+    });
+
+    const rates = await prepareExchangeRates();
+    expect(rates).toEqual(mockRates);
+    expect(GM_fetch).toHaveBeenCalled();
+    expect(setStorageValue).toHaveBeenCalledWith(storage_exchangerates, mockRates);
+  });
+
+  it('should handle fetch errors gracefully', async () => {
+    (getStorageValue as jest.Mock).mockResolvedValue(null);
+    (GM_fetch as jest.Mock).mockResolvedValueOnce({
+      ok: false,
+      status: 500
+    } as Response);
+
+    const rates = await prepareExchangeRates();
+    expect(rates).toBeNull();
+    expect(logError).toHaveBeenCalled();
+  });
+});