Since OpenZeppelin AccessControl's dynamic error messaging changes based on the sender's address and the checked role, it's been a challenge to write tests against it. As part of my solution, I wrote a utility function to automate the error message generation for my tests in Foundry Forge.

TestUtil.sol

function getEncodedAccessControlError(address account, bytes32 role)
  public
  pure
  returns (bytes memory)
{
  return
    abi.encodePacked(
      "AccessControl: account ",
      Strings.toHexString(uint160(account), 20),
      " is missing role ",
      Strings.toHexString(uint256(role), 32)
    );
}

// test in Forge
function testAccessControl() public {
  vm.startPrank(user);
  vm.expectRevert(
    getEncodedAccessControlError(user, ADMIN_ROLE)
  );
  contract.doSomethingThatRequiresAdminRole();
  vm.stopPrank();
}