Debugging, mounting.
Once the fighter jet's components and electronic equipment have been successfully debugged and everything is running normally, it's time to mount the engine, the most core component, onto the plane.
Engine installation is a very delicate job, and for relatively low-end fighter jets, it's easier to install the engine.
The installation of the WZ-A1 engine didn't take too much time on its first test flight, as only the main core interfaces were connected because of the mismatch between the fighter jet and the engine, which merely allowed for basic operations.
Now, switching to Warhawk-1 was different. Warhawk-1 was designed around the WZ-A1 engine, which also underwent functional improvements and adjustments to fit Warhawk-1. It can be said to be 'a perfect match,' where all functionalities and circuit interfaces would be utilized.