Englishfor English speakers
testify
—
verb
give testimony in a court of law
—
verb
(= evidence, show)
provide evidence for
The blood test showed that he was the father
Her behavior testified to her incompetence
for
Preposition
—
shows that something belongs to something else, or has a specific function
This cake is for you.
This is a net for catching fish.
—
For is used to show the reason for something
He was angry, for he had never been called such terrible names before.
for
Subordinator
—
For introduces a clause with a subject and a to-infinitive
It's not good for you to be too relaxed.