Error Transaction Failed when calling EndLottery function which uses ChainLink Oracle to get random number

[myhendry]

Hi. I am trying to do a lottery contract using hardhat and chainlink

Issues
I get this cryptic error message without any specific error message. below is a portion of the long error. i wonder if anyone has encounter this error before and point me in the direction to go toward resolving this error

The error occur when I call the endLottery() function. The other functions before this work fine on rinkeby network. I have a separate test using mocks and it is working fine hence I believe my solidity code should be fine. I have reproduced the solidity codes below just in case. I have also funded the smart contract with Link tokens in order to use the Chainlink oracle

const LinkToken = new ethers.Contract(link_token, abi, signer); tx = await LinkToken.transfer(lottery.address, 1000000000000000);

appreciate if someone can help advise on this. Thanks

Error Message
Error: transaction failed (transactionHash="0xbc55f0d34681e8b90d03cfc47316f7c2986247c62fa3560786121973e2d0522f", transaction={"hash":"0xbc55f0d34681e8b90d03cfc47316f7c298624... "logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","blockHash":"0x53ef0d29ddca38a90c22f30c7f418d55acfef
Test

const abi = require("../LinkTokenABI.json");

describe.only("Lottery (Rinkeby)", function () {
  let lottery;
  let admin;
  let player1;
  let player2;
  let result;
  let signer;

  signer = new ethers.Wallet(process.env.PRIVATE_KEY_RINKEBY, ethers.provider);
  // console.log("signer", signer);
  let tx;

  const price_feed_address = "0x8A753747A1Fa494EC906cE90E9f37563A8AF630e";
  const vrf_coordinator = "0xb3dCcb4Cf7a26f6cf6B120Cf5A73875B7BBc655B";
  const link_token = "0x01BE23585060835E02B77ef475b0Cc51aA1e0709";
  const keyhash =
    "0x2ed0feb3e7fd2022120aa84fab1945545a9f2ffc9076fd6156fa96eaff4c1311";
  const fee = 1000000000000000;

  before(async () => {
    [admin, player1, player2] = await ethers.getSigners();
    //console.log(admin.address, player1.address, player2.address);
    //signer = ethers.provider.getSigner();
  });

  describe("Return Lottery Results", async function () {
    it("Should return lottery", async function () {
      const Lottery = await ethers.getContractFactory("Lottery");
      lottery = await Lottery.deploy(
        price_feed_address,
        vrf_coordinator,
        link_token,
        fee,
        keyhash
      );
      await lottery.deployed();
      console.log("lottery address", lottery.address);

      console.log("fee", await lottery.fee());
      console.log("usdEntryFee", await lottery.usdEntranceFee());
      console.log(
        "getEntranceFee",
        await lottery.connect(admin).getEntranceFee()
      );

      const LinkToken = new ethers.Contract(link_token, abi, signer);
      tx = await LinkToken.transfer(lottery.address, 1000000000000000);
      await tx.wait();

      tx = await lottery.connect(admin).startLottery();
      await tx.wait();
      console.log("lottery_state", await lottery.lotteryState());

      tx = await lottery.connect(player1).enter({
        value: ethers.utils.parseEther("0.02"),
      });
      await tx.wait();

      tx = await lottery.connect(player2).enter({
        value: ethers.utils.parseEther("0.02"),
      });
      await tx.wait();

      console.log("players", await lottery.getPlayers());

      const balance1 = await ethers.provider.getBalance(lottery.address);
      const ether_balance_lottery_start = ethers.utils.formatEther(balance1);
      console.log("ether_balance_lottery_start", ether_balance_lottery_start);

      tx = await lottery.endLottery();
      const receipt = await tx.wait();
      console.log("lottery_state", await lottery.lotteryState());

      // const requestId = receipt.events[0].topics[1];
      // console.log("requestId", requestId);
    });

Lottery.sol

// Ends the lottery and gets a random number from the VRF coordinator.
    function endLottery() public onlyOwner {
        require(lotteryState == LOTTERY_STATE.OPEN, "Lottery is not open.");
        require(
            LINK.balanceOf(address(this)) >= fee,
            "Not enough LINK - fill contract with faucet"
        );
        lotteryState = LOTTERY_STATE.CALCULATING_WINNER;
        bytes32 requestId = requestRandomness(keyhash, fee);
        emit RequestedRandomNumber(requestId);
    }

    function getPlayers() public view returns (address payable[] memory) {
        return players;
    }

    // Callback function called by the VRF coordinator when the random number is returned.
    function fulfillRandomness(bytes32 _requestId, uint256 _randomness)
        internal
        override
    {
        require(
            lotteryState == LOTTERY_STATE.CALCULATING_WINNER,
            "Lottery is not in the calculating winner state."
        );
        require(_randomness > 0, "A random number was not found.");
        uint256 winnerIndex = _randomness % players.length;
        latestWinner = players[winnerIndex];
        latestWinner.transfer(address(this).balance);
        players = new address payable[](0);
        lotteryState = LOTTERY_STATE.CLOSED;
        latestRandomNumber = _randomness;
    }
}

[alcuadrado]

That's a typical error when a transaction fails in a network that's not Hardhat Network. We can't help you, as this is not a problem with Hardhat, but with your contract. You can dry-run your tx before sending it using ethers' staticCalls, and you'll get the revert reason doing that.

[myhendry]

Thanks for the advise. Appreciate. I will give it a try