You would have to remove the rail to test them, all at once. When you have all 4 out you can unplug the coil pack and turn the engine over. Put a piece of card under the injectors and a fairly good idea can be had of how well they are working. Card should show good spray pattern, not drippy or un-even.
Stuff like this is easy if you make sure you spend time doing it correctly, there is no harm in giving it a go, just remember all parts are designed to come away with relative easy so no snapping or anything!! Bit of rubber grease on seal to ease injectors back in