fluxswap/test/FluxPair.t.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.36;

import {Test} from "forge-std/Test.sol";
import {FluxFactory} from "../src/FluxFactory.sol";
import {FluxPair} from "../src/FluxPair.sol";
import {TestErc20} from "../src/TestErc20.sol";
import {IFluxCallee} from "../src/interfaces/IFluxCallee.sol";

contract ReentrantSwapper is IFluxCallee {
    FluxPair private pair;

    constructor(FluxPair pairAddress) {
        pair = pairAddress;
    }

    function fluxCall(address, uint256, uint256, bytes calldata) external {
        pair.swap(0, 1, address(this), "");
    }
}

contract FluxPairTest is Test {
    address private constant receiver = address(0xBEEF);

    FluxFactory private factory;
    FluxPair private pair;
    TestErc20 private token0;
    TestErc20 private token1;

    uint256 private initialLp;

    function setUp() public {
        factory = new FluxFactory(address(this));
        TestErc20 tokenA = new TestErc20("Alpha", "ALPHA", 1_000_000e18);
        TestErc20 tokenB = new TestErc20("Beta", "BETA", 1_000_000e18);
        address pairAddress = factory.createPair(address(tokenA), address(tokenB));
        pair = FluxPair(pairAddress);
        token0 = TestErc20(pair.token0());
        token1 = TestErc20(pair.token1());

        token0.transfer(pairAddress, 100e18);
        token1.transfer(pairAddress, 400e18);
        initialLp = pair.mint(address(this));
    }

    function testInitialMint() public view {
        assertEq(initialLp, 199999999999999999000);
        assertEq(pair.balanceOf(address(this)), 199999999999999999000);
        assertEq(pair.totalSupply(), 200e18);
        assertEq(pair.balanceOf(address(0)), 1000);
        (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
        assertEq(reserve0, 100e18);
        assertEq(reserve1, 400e18);
    }

    function testProportionalMint() public {
        token0.transfer(address(pair), 50e18);
        token1.transfer(address(pair), 200e18);
        uint256 minted = pair.mint(receiver);
        assertEq(minted, 100e18);
        assertEq(pair.balanceOf(receiver), 100e18);
        assertEq(pair.totalSupply(), 300e18);
        (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
        assertEq(reserve0, 150e18);
        assertEq(reserve1, 600e18);
    }

    function testSwapMovesReservesAndKeepsInvariant() public {
        uint256 expectedOut = 36264435755205965263;
        uint256 kBefore = uint256(100e18) * 400e18;

        token0.transfer(address(pair), 10e18);
        pair.swap(0, expectedOut, receiver, "");

        assertEq(token1.balanceOf(receiver), expectedOut);
        (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
        assertEq(reserve0, 110e18);
        assertEq(reserve1, 363735564244794034737);
        assertGt(uint256(reserve0) * uint256(reserve1), kBefore);
    }

    function testSwapRevertsWhenInvariantBroken() public {
        token0.transfer(address(pair), 10e18);
        vm.expectRevert(bytes("Flux: K"));
        pair.swap(0, 36264435755205965263 + 1e15, receiver, "");
    }

    function testSwapRevertsWithoutInput() public {
        vm.expectRevert(bytes("Flux: INSUFFICIENT_INPUT_AMOUNT"));
        pair.swap(0, 1e18, receiver, "");
    }

    function testBurnReturnsProportional() public {
        uint256 lp = pair.balanceOf(address(this));
        pair.transfer(address(pair), lp);
        (uint256 amount0, uint256 amount1) = pair.burn(receiver);

        assertEq(amount0, 99999999999999999500);
        assertEq(amount1, 399999999999999998000);
        assertEq(token0.balanceOf(receiver), 99999999999999999500);
        assertEq(token1.balanceOf(receiver), 399999999999999998000);
        assertEq(pair.totalSupply(), 1000);
    }

    function testSkimSendsExcessAndKeepsReserves() public {
        token0.transfer(address(pair), 5e18);
        pair.skim(receiver);
        assertEq(token0.balanceOf(receiver), 5e18);
        (uint112 reserve0,,) = pair.getReserves();
        assertEq(reserve0, 100e18);
    }

    function testSyncAdoptsBalances() public {
        token0.transfer(address(pair), 5e18);
        pair.sync();
        (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
        assertEq(reserve0, 105e18);
        assertEq(reserve1, 400e18);
    }

    function testPriceAccumulatorGrowsOverTime() public {
        assertEq(pair.price0CumulativeLast(), 0);
        vm.warp(block.timestamp + 3600);
        pair.sync();
        assertGt(pair.price0CumulativeLast(), 0);
        assertGt(pair.price1CumulativeLast(), 0);
    }

    function testReentrancyLockBlocksSwap() public {
        ReentrantSwapper attacker = new ReentrantSwapper(pair);
        token0.transfer(address(pair), 10e18);
        vm.expectRevert(bytes("Flux: LOCKED"));
        pair.swap(0, 1e18, address(attacker), "0x01");
    }
}