Pancakeswap swap fails with INSUFFICIENT_OUTPUT_AMOUNT error

Question

I'm trying to make a swap on the Binance testnet using Pancakeswap. I keep getting an INSUFFICIENT_OUTPUT_AMOUNT error and I have no idea why. Here is my code:

const ethers = require('ethers');

const WBNB = "0xae13d989dac2f0debff460ac112a837c89baa7cd"; 
const BUSD = "0xaB1a4d4f1D656d2450692D237fdD6C7f9146e814";

const router = "0x9Ac64Cc6e4415144C455BD8E4837Fea55603e5c3";

const provider = new ethers.providers.JsonRpcProvider("my.provider.url");
const wallet = new ethers.Wallet("myPrivateKey");
const signer = wallet.connect(provider);

const routerContract = new ethers.Contract(
    router,
    [
        'function getAmountsOut(uint amountIn, address[] memory path) public view returns(uint[] memory amounts)',
        'function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)'
    ],
    signer
);

const busdContract = new ethers.Contract(
    BUSD,
    [
        'function approve(address spender, uint256 amount) external returns (bool)'
    ],
    signer
)

async function main() {

    const BUSDamountIn = ethers.utils.parseUnits('100', 18);
    let amounts = await routerContract.getAmountsOut(BUSDamountIn, [BUSD, WBNB]);
    const WBNBamountOutMin = 0;

    console.log(ethers.utils.formatEther(BUSDamountIn));
    console.log(ethers.utils.formatEther(WBNBamountOutMin));

    const approveTx = await busdContract.approve(
        router,
        BUSDamountIn
    );
    let reciept = await approveTx.wait();
    console.log(reciept);

    const swapTx = await routerContract.swapExactTokensForTokens(
        BUSDamountIn,
        WBNBamountOutMin,
        [BUSD, WBNB],
        wallet.address,
        Date.now() + 1000 * 60 * 10,
        {gasLimit: 250000}
    )

    receipt = await swapTx.wait();
    console.log(receipt);
}

main().then().finally(() => {});

The first transaction that approves the token spending amount to the router works fine, but the swap itself fails.

Ethers.js throws the following error:

Error: transaction failed [ See: https://links.ethers.org/v5-errors-CALL_EXCEPTION ]

On the bsc scanner the error code is:

Fail with error 'PancakeRouter: INSUFFICIENT_OUTPUT_AMOUNT'

The INSUFFICIENT_OUTPUT_AMOUNT error does not make any sense to me because the WBNBamountOutMin is set to 0 so any amount out should be ok.

Here is the example transaction: https://testnet.bscscan.com/tx/0xa87783c39e3787fbbf99236da631abe3991318523d1b3f0e87660eda1a9dfdce

Can anyone explain to me why this swap does not work?

Answer 1

This means that the pool doesn't have enough liquidity to return the output token (or even not liquidity at all).