diff --git a/src/services/sources/stellarDex.js b/src/services/sources/stellarDex.js
index 7ea535c..8e2c43d 100644
--- a/src/services/sources/stellarDex.js
+++ b/src/services/sources/stellarDex.js
@@ -1,4 +1,4 @@
-const { Server } = require('stellar-sdk');
+const { Asset, Horizon } = require('stellar-sdk');
 const config = require('../../config');
 const logger = require('../../logger');
 
@@ -6,66 +6,78 @@ let server = null;
 
 function getServer() {
   if (!server) {
-    server = new Server(config.stellar.horizonUrl);
+    server = new Horizon.Server(config.stellar.horizonUrl);
   }
   return server;
 }
 
-const XLM_ASSET = { native: true };
+function xlmAsset() {
+  return Asset.native();
+}
 
-async function fetchPrice(assetCode, issuer) {
-  try {
-    const horizon = getServer();
+function usdcAsset() {
+  return new Asset('USDC', config.stellar.usdcIssuer);
+}
 
-    let base;
-    let counter;
+function issuedAsset(assetCode, issuer) {
+  return new Asset(assetCode, issuer);
+}
 
-    if (!issuer || assetCode === 'XLM') {
-      base = XLM_ASSET;
-      counter = { code: 'USDC', issuer: config.stellar.usdcIssuer };
-    } else {
-      base = { code: assetCode, issuer };
-      counter = XLM_ASSET;
-    }
+function midpointFromOrderBook(orderBook) {
+  const bidPrice = orderBook.bids?.[0]?.price;
+  const askPrice = orderBook.asks?.[0]?.price;
+  const bestBid = bidPrice !== undefined ? parseFloat(bidPrice) : null;
+  const bestAsk = askPrice !== undefined ? parseFloat(askPrice) : null;
+  const hasBid = Number.isFinite(bestBid) && bestBid > 0;
+  const hasAsk = Number.isFinite(bestAsk) && bestAsk > 0;
+
+  if (hasBid && hasAsk) return (bestBid + bestAsk) / 2;
+  if (hasBid) return bestBid;
+  if (hasAsk) return bestAsk;
+  return null;
+}
+
+async function fetchOrderBookMidpoint(horizon, base, counter) {
+  const orderBook = await horizon.orderbook(base, counter).limit(1).call();
+  return midpointFromOrderBook(orderBook);
+}
 
-    const orderBook = await horizon.orderbook(base, counter === XLM_ASSET ? undefined : counter).limit(1).call();
+async function fetchPrice(assetCode, issuer) {
+  try {
+    const horizon = getServer();
+    const normalizedCode = assetCode.toUpperCase();
 
-    if (!orderBook.bids || orderBook.bids.length === 0) {
+    if (!issuer && normalizedCode !== 'XLM') {
+      logger.debug('Stellar DEX issuer required for issued asset', { assetCode });
       return null;
     }
 
-    const bestBid = parseFloat(orderBook.bids[0].price);
-
-    if (!issuer || assetCode === 'XLM') {
-      const xlmUsdcPrice = bestBid;
-      const xlmUsd = await getXlmUsdPrice(horizon);
-      if (xlmUsd === null) return null;
-      return xlmUsdcPrice * xlmUsd;
+    if (normalizedCode === 'XLM') {
+      return await fetchOrderBookMidpoint(horizon, xlmAsset(), usdcAsset());
     }
 
-    return bestBid;
+    const assetInXlm = await fetchOrderBookMidpoint(
+      horizon,
+      issuedAsset(normalizedCode, issuer),
+      xlmAsset()
+    );
+    if (assetInXlm === null) return null;
+
+    const xlmUsd = await getXlmUsdPrice(horizon);
+    if (xlmUsd === null) return null;
+    return assetInXlm * xlmUsd;
   } catch (err) {
     logger.warn('Stellar DEX price fetch failed', { assetCode, issuer, error: err.message });
-    return null;
+    throw err;
   }
 }
 
 async function getXlmUsdPrice(horizon) {
   try {
-    const usdcIssuer = config.stellar.usdcIssuer;
-    const orderBook = await horizon
-      .orderbook(XLM_ASSET, { code: 'USDC', issuer: usdcIssuer })
-      .limit(1)
-      .call();
-
-    if (!orderBook.bids || orderBook.bids.length === 0) {
-      return null;
-    }
-
-    return parseFloat(orderBook.bids[0].price);
+    return await fetchOrderBookMidpoint(horizon, xlmAsset(), usdcAsset());
   } catch (err) {
     logger.warn('XLM/USDC price fetch failed', { error: err.message });
-    return null;
+    throw err;
   }
 }
 
diff --git a/test/stellarDex.test.js b/test/stellarDex.test.js
new file mode 100644
index 0000000..597e97d
--- /dev/null
+++ b/test/stellarDex.test.js
@@ -0,0 +1,176 @@
+'use strict';
+
+const mockOrderbook = jest.fn();
+const mockServer = { orderbook: mockOrderbook };
+const mockServerConstructor = jest.fn(() => mockServer);
+const mockNativeAsset = { native: true };
+const mockAsset = jest.fn(function Asset(code, issuer) {
+  return { code, issuer };
+});
+mockAsset.native = jest.fn(() => mockNativeAsset);
+
+jest.mock('stellar-sdk', () => ({
+  Horizon: {
+    Server: mockServerConstructor,
+  },
+  Asset: mockAsset,
+}));
+
+jest.mock('../src/logger', () => ({
+  info: jest.fn(),
+  warn: jest.fn(),
+  error: jest.fn(),
+  debug: jest.fn(),
+}));
+
+const config = require('../src/config');
+const logger = require('../src/logger');
+const stellarDex = require('../src/services/sources/stellarDex');
+
+const ISSUER = 'G'.padEnd(56, 'A');
+
+function queueOrderBook(result) {
+  const call = jest.fn();
+  if (result instanceof Error) {
+    call.mockRejectedValue(result);
+  } else {
+    call.mockResolvedValue(result);
+  }
+
+  const limit = jest.fn(() => ({ call }));
+  mockOrderbook.mockImplementationOnce(() => ({ limit }));
+  return { call, limit };
+}
+
+beforeEach(() => {
+  mockOrderbook.mockReset();
+  mockServerConstructor.mockClear();
+  mockAsset.mockClear();
+  mockAsset.native.mockClear();
+  logger.warn.mockClear();
+  logger.debug.mockClear();
+});
+
+describe('Stellar DEX source', () => {
+  test('returns midpoint of best ask and best bid for issued assets', async () => {
+    queueOrderBook({
+      bids: [{ price: '2.0' }],
+      asks: [{ price: '2.2' }],
+    });
+    queueOrderBook({
+      bids: [{ price: '0.10' }],
+      asks: [{ price: '0.12' }],
+    });
+
+    await expect(stellarDex.fetchPrice('TEST', ISSUER)).resolves.toBeCloseTo(0.231);
+
+    expect(mockOrderbook).toHaveBeenNthCalledWith(
+      1,
+      { code: 'TEST', issuer: ISSUER },
+      mockNativeAsset
+    );
+    expect(mockOrderbook).toHaveBeenNthCalledWith(
+      2,
+      mockNativeAsset,
+      { code: 'USDC', issuer: config.stellar.usdcIssuer }
+    );
+  });
+
+  test('uses best bid when asks are empty', async () => {
+    queueOrderBook({
+      bids: [{ price: '0.11' }],
+      asks: [],
+    });
+
+    await expect(stellarDex.fetchPrice('XLM')).resolves.toBe(0.11);
+  });
+
+  test('uses best ask when bids are empty', async () => {
+    queueOrderBook({
+      bids: [],
+      asks: [{ price: '0.12' }],
+    });
+
+    await expect(stellarDex.fetchPrice('XLM')).resolves.toBe(0.12);
+  });
+
+  test('returns null when asks and bids are empty', async () => {
+    queueOrderBook({
+      bids: [],
+      asks: [],
+    });
+
+    await expect(stellarDex.fetchPrice('XLM')).resolves.toBeNull();
+  });
+
+  test('returns null for issued assets when issuer is missing', async () => {
+    await expect(stellarDex.fetchPrice('USDC')).resolves.toBeNull();
+
+    expect(mockOrderbook).not.toHaveBeenCalled();
+    expect(logger.debug).toHaveBeenCalledWith(
+      'Stellar DEX issuer required for issued asset',
+      { assetCode: 'USDC' }
+    );
+  });
+
+  test('throws when Horizon returns a non-200 error', async () => {
+    const error = new Error('Horizon request failed with status 500');
+    error.response = { status: 500 };
+    queueOrderBook(error);
+
+    await expect(stellarDex.fetchPrice('XLM')).rejects.toThrow('status 500');
+    expect(logger.warn).toHaveBeenCalledWith(
+      'Stellar DEX price fetch failed',
+      expect.objectContaining({ assetCode: 'XLM', error: error.message })
+    );
+  });
+
+  test('throws timeout errors from Horizon', async () => {
+    const error = new Error('timeout of 10000ms exceeded');
+    error.code = 'ECONNABORTED';
+    queueOrderBook(error);
+
+    await expect(stellarDex.fetchPrice('XLM')).rejects.toThrow('timeout');
+    expect(logger.warn).toHaveBeenCalledWith(
+      'Stellar DEX price fetch failed',
+      expect.objectContaining({ assetCode: 'XLM', error: error.message })
+    );
+  });
+
+  test('throws and logs when XLM/USD conversion lookup fails', async () => {
+    queueOrderBook({
+      bids: [{ price: '2.0' }],
+      asks: [{ price: '2.2' }],
+    });
+    const error = new Error('XLM/USDC lookup failed');
+    queueOrderBook(error);
+
+    await expect(stellarDex.fetchPrice('TEST', ISSUER)).rejects.toThrow(
+      'XLM/USDC lookup failed'
+    );
+    expect(logger.warn).toHaveBeenCalledWith('XLM/USDC price fetch failed', {
+      error: error.message,
+    });
+    expect(logger.warn).toHaveBeenCalledWith(
+      'Stellar DEX price fetch failed',
+      expect.objectContaining({ assetCode: 'TEST', issuer: ISSUER })
+    );
+  });
+
+  test('uses the native XLM/USDC orderbook for XLM without issuer', async () => {
+    queueOrderBook({
+      bids: [{ price: '0.11' }],
+      asks: [{ price: '0.12' }],
+    });
+
+    await expect(stellarDex.fetchPrice('XLM')).resolves.toBeCloseTo(0.115);
+
+    expect(mockOrderbook).toHaveBeenCalledTimes(1);
+    expect(mockAsset.native).toHaveBeenCalledTimes(1);
+    expect(mockAsset).toHaveBeenCalledWith('USDC', config.stellar.usdcIssuer);
+    expect(mockOrderbook).toHaveBeenCalledWith(
+      mockNativeAsset,
+      { code: 'USDC', issuer: config.stellar.usdcIssuer }
+    );
+  });
+});