pragma solidity 0.8.10;

import "ds-test/test.sol";

interface Vm {
  function mockCall(address,bytes calldata,bytes calldata) external;
}

contract MyContract {
  function outer() public returns (uint256) {
    return inner();
  }

  function inner() public returns (uint256) {
    return 5;
  }
}

contract MyContractTest is DSTest {
  MyContract c;
  Vm vm = Vm(address(bytes20(uint160(uint256(keccak256('hevm cheat code'))))));

  function testMock() public {
    c = new MyContract();
    assertEq(c.inner(), 5);
    assertEq(c.outer(), 5);

    uint256 _newVal = 10;
    vm.mockCall(address(c), abi.encodeWithSelector(c.inner.selector), abi.encode(_newVal));

    assertEq(c.inner(), _newVal); // passes
    assertEq(c.outer(), _newVal); // fails
  }
}