There are many ways to test weapons. We cannot doubt the capability of a weapon just because it hasn't been tested in combat. The Russian Tsar Bomba also hasn’t been tested in combat; does that mean we should doubt its power?
As for China’s military aircraft, the U.S. military has the most say. PLA’s various military aircraft and the U.S. military’s various aircraft frequently engage in different kinds of contests over the East China Sea and the South China Sea. All combat skills of military aircraft, except for firing, have been tested (chasing, dogfighting, stealth and counter-stealth, electronic jamming, heat flares, laser targeting, etc.). You can look up interviews with frontline U.S. military officers about these situations (ignore those office-bound fat cats; they are only serving political purposes and defense budgets).
The most important point is the people using these weapons. The same weapon can have completely different effects in different countries’ armed forces (many countries around the world are equipped with the same Rafale fighter jets; can you say they have the same combat power?).
A country in the Middle East, equipped with many very advanced weapons, however, they were defeated by the low-level weapons of the guerrillas. Can you say no to the weapons he purchased?
We cannot deny the weapon itself because of this.
