How to compare before and after balance of any address in while testing in hardhat?

Question

I was writing test script for a contract. I am stuck at a point where there is a claim function. whenever a user calls it, he gets the claimable ether, whatever available. The problem is when I compare the balance before and after calling the claim function, it doesn't match. One reason I can think of is the gas price that is being deducted. If this is the reason then how can I include the gas price amount in the calculation? What can be other reasons?

This is the test case.

      it("user1 can withdraw their funds", async () => {
      let balance1 = await ethers.provider.getBalance(participant1.address);
      await expect(bounty.connect(participant1).claimPrize()).to.be.fulfilled;
      expect(await ethers.provider.getBalance(participant1.address)).to.be.equal(balance1.add(ethers.utils.parseEther("2")));

    })

Answer 1

The gas price is the reason for the balance mismatch. When a user calls a function that requires gas, the gas is deducted from their account balance. This means that the amount of ether they receive after calling the function will be less than the amount they had before the function call.

Here try this updated code

it("user1 can withdraw their funds", async () => {
  let balance1 = await ethers.provider.getBalance(participant1.address);
  let tx = await bounty.connect(participant1).claimPrize();
  let receipt = await tx.wait();
  let gasCost = receipt.gasUsed.mul(receipt.gasPrice);
  expect(await ethers.provider.getBalance(participant1.address)).to.be.equal(balance1.add(ethers.utils.parseEther("2")).sub(gasCost));
})