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Use Case

Check if the constant product is maintained in an AMM pool. This is useful in cases where you want to make sure that the AMM pool is not manipulated.

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Explanation

The assertion checks if the constant product is maintained in an AMM pool after a transaction has been executed.

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Code Example

// SPDX-License-Identifier: MIT
pragma solidity 0.8.28;

import {Assertion} from "../../lib/credible-std/src/Assertion.sol";

// We assume Aerodrome style pool
interface IAmm {
    function getReserves() external view returns (uint256, uint256);

    function getK() external view returns (uint256);
}

contract ConstantProductAssertion is Assertion {
    IAmm public amm = IAmm(address(0xbeef));

    function fnSelectors() external pure override returns (bytes4[] memory assertions) {
        assertions = new bytes4[](1);
        assertions[0] = this.assertionConstantProduct.selector;
    }

    // Make sure that the product of the reserves is equal to the constant product
    // note: fees might have to be handled depending on the pool
    function assertionConstantProduct() external {
        ph.forkPostState(); // Fork the post state
        (uint256 reserve0, uint256 reserve1) = amm.getReserves();
        uint256 k = reserve0 * reserve1;
        require(k == amm.getK(), "Constant product does not hold");
    }
}
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