What is revealed by Tom Robinson's testimony?

Tom Robinson is innocent...

hahaha!yes, because he is proven physically incapable of beating up Mayella. Tom Robinson's testimony shows that he is honest and concerned for the welfare of others, which shows he is innocent, and indirectly saying that Bob Ewell the drunkard father, beat up Mayella

Much is revealed . . .

His own character as a decent, humble, respectable man.

Mayella's scheme to get the children off the property and lure Tom into the house.

Bob's history of abuse. "She says what her daddy do to her don't count" is a key line in this novel.