function strategyWithdraw(uint256 _amount, IERC20 _token) external override {
  ...
  uint256 balanceBefore = _token.balanceOf(address(this));
  ps.strategy.withdraw(_amount);
  require(balanceBefore.add(_amount) == _token.balanceOf(address(this)), "REASON");
  ps.stakeBalance = ps.stakeBalance.add(_amount);
}

function strategyWithdrawAll(IERC20 _token) external override {
  PoolStorage.Base storage ps = baseData();
  _enforceGovPool(ps);
  _enforceStrategy(ps);

  uint256 balanceBefore = _token.balanceOf(address(this));
  ps.strategy.withdrawAll();
  // alternatively, verify amount returned by withdrawAll() method
  uint256 amount = _token.balanceOf(address(this)).sub(balanceBefore);
  ps.stakeBalance = ps.stakeBalance.add(amount);
  }
