// PASS
function testThings() {
  Contract inner = new Contract();
  NestedContract target = new NestedContract(inner);
  vm.expectCall(address(inner), abi.encodeWithSelector(inner.bar.selector), 2);
  inner.bar(); // call bar directly. Counts as 1 of two calls expected.
  target.baz(); // will call bar internally. This counts as 2 of two calls expected. expectCall is fulfilled.
}

// FAIL
function testOne() {
  Contract inner = new Contract();
  NestedContract target = new NestedContract(inner);
  vm.expectCall(address(inner), abi.encodeWithSelector(inner.bar.selector), 1);
  inner.bar(); // call bar directly. This does not get counted, as this is a test-level call. It should be abstracted into another call.
}

// PASS
function testOne() {
  Contract inner = new Contract();
  NestedContract target = new NestedContract(inner);
  vm.expectCall(address(inner), abi.encodeWithSelector(inner.bar.selector), 1);
  target.baz(); // will call bar internally, therefore works.
}

contract NestedContract {
  Contract public inner;

  constructor(Contract _inner) {
    inner = _inner;
  }
  function baz() public {
    inner.bar(); // call bar 
  }
}