About Handler.t.sol in TSwap.

[GaurangBharadava]

After a long time i have continued my security course.
So the thing i am not understanding is deposit function in Handler.t.sol.

function deposit(uint256 wethAmount) public {
        wethAmount = bound(wethAmount,0 , type(uint64).max);
        startingY = weth.balanceOf(address(this));
        startingX = poolToken.balanceOf(address(this));
        expectedDeltaY = wethAmount;
        expectedDeltaX = pool.getPoolTokensToDepositBasedOnWeth(startingY);

        vm.startPrank(liquidityProvider);
        weth.mint(liquidityProvider, wethAmount);
        poolToken.mint(liquidityProvider, expectedDeltaX);
        weth.approve(address(pool), type(uint256).max);
        poolToken.approve(address(pool), type(uint256).max);
        pool.deposit(wethAmount, 0, expectedDeltaX, uint64(block.timestamp));
        vm.stopPrank();

        uint256 endingY = weth.balanceOf(address(this));
        uint256 endingX = poolToken.balanceOf(address(this));

        actualDeltaY = int256(endingY) - int256(startingY);
        actualDeltaX = int256(endingX) - int256(startingX);
    }

like why we are checking balance of handler contract to get starting and ending value of X and Y. an also why we are approving the pool to deposite tokens amount.

[EngrPips]

We are checking the pool balance and getting the started and ending values to ensure that what was deposited was what we intended to deposit. And we also need to approve the pool so that the pool will be able to take from us the tokens that we want to deposit to the pool.

Ask questions if anything is confusing.

[GaurangBharadava]

Like that i understood. but for checking the pool balance why we are checking for address(this)?

[EngrPips]

I am unsure where you get your code from but the below is the code I have

function deposit(uint256 wethAmount) public {
        wethAmount = bound(
            wethAmount,
            pool.getMinimumWethDepositAmount(),
            weth.balanceOf(address(pool))
        );

        startingY = int256(poolToken.balanceOf(address(pool)));
        startingX = int256(weth.balanceOf(address(pool)));

        expectedDeltaX = int256(wethAmount);
        expectedDeltaY = int256(
            pool.getPoolTokensToDepositBasedOnWeth(wethAmount)
        );

        vm.startPrank(liquidityProvider);
        weth.mint(liquidityProvider, wethAmount);
        poolToken.mint(liquidityProvider, uint256(expectedDeltaX));
        weth.approve(address(pool), type(uint256).max);
        poolToken.approve(address(pool), type(uint256).max);

        // Deposit
        pool.deposit(
            wethAmount,
            0,
            uint256(expectedDeltaX),
            uint64(block.timestamp)
        );
        vm.stopPrank();

        uint256 endingX = poolToken.balanceOf(address(pool));
        uint256 endingY = weth.balanceOf(address(pool));

        // sell tokens == x == poolTokens
        actualDeltaY = int256(endingX) - int256(startingY);
        actualDeltaX = int256(endingY) - int256(startingX);
    }

I was getting the balance of the pool the whole time, while you were getting the balance of the handler contract the whole time. Is that intended or is my code wrong?

[GaurangBharadava]

I was follow along with cyfrin course. But i will check, I think your code is right

[EngrPips]

Yeah, check it out.