Handling a Solidity Library function that reverts

LibRevert.t.sol

// SPDX-License-Identifier: Unlicense
pragma solidity 0.8.10;

import "ds-test/test.sol";

interface Hevm {
    // Expects an error on next call
    function expectRevert(bytes calldata) external;
}

error MyError();

library MyLib {
  function foo() internal {
    revert MyError();
  }
}

contract MyTest is DSTest {
    Hevm internal constant hevm = Hevm(HEVM_ADDRESS);

    function testExample() public {
        hevm.expectRevert(abi.encodeWithSignature("MyError()"));
        MyLib.foo();
    }
}

LibRevertFixed.t.sol

// SPDX-License-Identifier: Unlicense
pragma solidity 0.8.10;

import "ds-test/test.sol";

interface Hevm {
    // Expects an error on next call
    function expectRevert(bytes calldata) external;
}

error MyError();

library MyLib {
  function foo() internal {
    revert MyError();
  }
}

contract MyLibWrapper {
    function foo() public {
        MyLib.foo();
    }
}

contract MyTestFixed is DSTest {
    Hevm internal constant hevm = Hevm(HEVM_ADDRESS);

    MyLibWrapper libWrapper;

    function setUp() public {
        libWrapper = new MyLibWrapper();
    }

    function testExample() public {
        hevm.expectRevert(abi.encodeWithSignature("MyError()"));
        libWrapper.foo();
    }
}