Do you have a digital multi-meter? If so, you can do a simple load test on the new alt. If not, a dome light test can be used instead, to get a fairly good ballpark estimate. Battery needs to be fully charged in order for the load test to be meaningful. The new alt might be bad out of the box, and it wouldn't be the first time that ever happened.
If those little Chinese kids don't work fast enough, they don't make enough Yen to buy dinner