Testing Your Integration

How to test your CoW Protocol integration on Sepolia testnet, using the staging API, and common testing pitfalls to avoid.

Testnet: Sepolia

CoW Protocol is deployed on Sepolia for testing. All contracts share the same addresses as mainnet:

Contract	Address
GPv2Settlement	0x9008D19f58AAbD9eD0D60971565AA8510560ab41
GPv2VaultRelayer	0xC92E8bdf79f0507f65a392b0ab4667716BFE0110

API endpoint

https://api.cow.fi/sepolia/api/v1/

SDK configuration

import { SupportedChainId, TradingSdk } from '@cowprotocol/sdk-trading'

const sdk = new TradingSdk({
  chainId: SupportedChainId.SEPOLIA,
  appCode: 'my-app-testing',
}, {}, adapter)

Important: Sepolia has limited solver participation

Many solvers do not participate on Sepolia. This means:

• Orders may take longer to fill or expire unfilled
• Liquidity is thin — not all token pairs are tradeable
• Price quality is lower than mainnet

This is normal testnet behavior, not a bug in your integration.

Tips for successful testnet orders

1. Use wider limit prices — set slippage to 5-10% instead of the typical 0.5-1%
2. Stick to common test pairs — WETH, USDC, and COW token have the most testnet liquidity
3. Use longer validity — set validFor to 1800+ seconds (30 min) to give solvers more batches
4. Check the explorer — verify your order appears at https://explorer.cow.fi/sepolia/orders/{uid}

Getting test tokens

• Sepolia ETH: Use a faucet like sepoliafaucet.com or Alchemy Sepolia Faucet
• Test ERC-20s: Wrap ETH to WETH, then swap for test tokens on CoW Swap (Sepolia) or Uniswap (Sepolia)

Staging API (barn)

For testing against mainnet data without affecting production, use the staging (“barn”) API:

https://barn.api.cow.fi/mainnet/api/v1/

The barn API:

• Runs the same code as production, deployed ahead of releases
• Uses real mainnet tokens and liquidity
• Has a separate solver competition (solvers may behave differently)
• Is useful for testing mainnet integrations before going live

Orders submitted to barn are real orders on mainnet. They use real tokens and will settle on-chain if filled. Use barn for integration testing with small amounts, not as a sandbox.

SDK with barn

const parameters: TradeParameters = {
  env: 'staging', // Uses barn API
  kind: OrderKind.SELL,
  // ... rest of parameters
}

Recommended testing workflow

1. Start on Sepolia — verify your signing, order creation, and status polling logic works end-to-end
2. Move to barn (mainnet staging) — test with real liquidity and solver competition using small amounts
3. Go to production — switch to api.cow.fi/mainnet with production amounts

Common testnet issues

Issue	Cause	Fix
Order expires unfilled	Limited solvers on Sepolia	Widen slippage, use longer validity, try WETH/USDC pair
NoLiquidity error	Token pair has no testnet pools	Use well-known test tokens (WETH, USDC)
SellAmountDoesNotCoverFee	Gas costs high relative to small test amounts	Increase the sell amount
Order shows presignaturePending	PreSign transaction not confirmed	Wait for Sepolia block confirmation, check tx hash
Different results than mainnet	Different solver set and liquidity	Expected — use barn for mainnet-equivalent testing

Related resources

• API Integration Guide — Full API integration walkthrough
• Error Reference — All API error codes and fixes
• Rate Limits — Rate limits apply equally on testnet