Update tests for callback.js

maybe check res.send was called?

`callbackFunction(req, res, function() {});`

```js
    var res = {
      send: function(statusCode, tmp, headers) {
        statusCode.should.eql(302);
        headers.should.have.property('location', tempToken.returnTo + "?state=success");
        done()
      }
    };
```