Error: VM Exception while processing transaction: reverted with reason string 'ERC20: insufficient allowance' at TokenA._spendAllowance (@openzeppelin/contracts/token/ERC20/ERC20.sol:337) at TokenA.transferFrom (@openzeppelin/contracts/token/ERC20/ERC20.sol:164)

[Benrockiee]

When i try to run test for my DEX contracts, i get this error

Error: VM Exception while processing transaction: reverted with reason string 'ERC20: insufficient allowance'
    at TokenA._spendAllowance (@openzeppelin/contracts/token/ERC20/ERC20.sol:337)
    at TokenA.transferFrom (@openzeppelin/contracts/token/ERC20/ERC20.sol:164)

This is my test script

const { expect } = require("chai")
const { ethers } = require("hardhat")

describe("Xchange", function () {
  let xchange
  let owner
  let feeAccounts
  //let Amount

  beforeEach(async function () {
    ;[owner, ...feeAccounts] = await ethers.getSigners()

    const Xchange = await ethers.getContractFactory("Xchange")
    xchange = await Xchange.deploy(
      feeAccounts.map((account) => account.address),
      25,
      20
    )
    await xchange.deployed()
  })

  it("should swap tokens and distribute fees correctly", async function () {
    const TokenA = await ethers.getContractFactory("TokenA")
    const tokenA = await TokenA.deploy()
    await tokenA.deployed()

    const TokenB = await ethers.getContractFactory("TokenB")
    const tokenB = await TokenB.deploy()
    await tokenB.deployed()

    // const tokenAmount = ethers.utils.parseEther("1")
    const tokenAmount = ethers.utils.parseUnits("1", "ether")

    await tokenA.transfer(xchange.address, tokenAmount)

    await tokenA.approve(xchange.address, tokenAmount)
    /* const tokenOwnerBalance = await tokenA.balanceOf(owner.address)
    if (tokenOwnerBalance.lt(tokenAmount)) {
      throw new Error("Insufficient token balance")
    }*/

    await tokenA.transferFrom(owner.address, xchange.address, tokenAmount)
    await xchange.swapTokens(tokenA.address, tokenB.address, tokenAmount)

    const tokenABalance = await tokenA.balanceOf(xchange.address)
    expect(tokenABalance).to.equal(0)

    const tokenBBalance = await tokenB.balanceOf(xchange.address)
    expect(tokenBBalance).to.be.above(0)

    const ethBalance = await ethers.provider.getBalance(xchange.address)
    expect(ethBalance).to.be.above(0)

    const feeShare = ethBalance.div(feeAccounts.length)
    for (const account of feeAccounts) {
      const accountBalanceBefore = await ethers.provider.getBalance(
        account.address
      )
      await xchange.connect(account).splitFees()
      const accountBalanceAfter = await ethers.provider.getBalance(
        account.address
      )
      expect(accountBalanceAfter).to.equal(accountBalanceBefore.add(feeShare))
    }
  })
})

[alymurtazamemon]

@Benrockiee Make sure you approve the tokens to your DEX so it can transfer to using transferFrom.