What is testimony?

"How much you have done,
Yahweh, my God - your wonders,
your plans for us - you have no equal.
I will proclaim and speak of them;
they are beyond number."
- Psalm 40:5

To man it is a message of grace
To God it is a praise to grace

When man gives testimony to man
Christ promises to give testimony to God.

- Dr. Robert Witty,
The Christian Testimony