Testing Warcraft itself or Warcraft 3 Viewer can be used to test models. Before testing with either of these methods, you should convert to MDX. This will tell you if you have errors, lower the file size, and allow the viewer to look at it at all. Just use Yobguls' File Converter to convert. Testing with Warcraft 3 Viewer This is very much simpler and faster but doesn't always give exactly the correct result. For the most part, it is the best choice for testing quick edits. Just load the the viewer, click "Open MDX", and browse to select the MDX. Testing with Warcraft: It is always a good idea to do this before releasing a final model. Open the World Editor. Open the Import Manager. Click the import button and browse to select your MDX. Save. Close the editor. (Before actually being able to see a newly imported model, you will almost always have to close and reopen.) Reopen the editor and your map. Open the Object Editor and change the Art-Model field of any unit to that of the imported model. Place the unit on the map.