How would you know? Probably because your testes were small or tiny would make you suspicious. If you were trying to make a baby... a sperm count would settle it. The idea that one could use gear as birth control has been around for a long time. But many who thought that they were 'safe' from pregnancy found that not to be true. The "male pill" was going to be like that but has not become a product.
In many cases, testes can be recovered with HCG and all of the other PCT candidates. It is only when the testes are very small/tiny for a long time that permanent changes to structure occur [atrophy].
The testes normally have concentrations of T that are around 100 times greater than in the blood.
That is needed to make sperm. So TRT alone would not make sperm. One needs LH or HCG to get the testes working to create those high intratesticular testosterone levels.
Research showed that on average, 250iu of HCG SQ EOD restored intratesticular T levels to those high baseline values [in men where were fully LH suppressed with 200mg test cyp per week].