'Testimony is True' in the Bible

If I testify concerning myself, my testimony is true; for I know whence I came, and whither I go. You know not whence I come, or whither I go.

And He having seen hath testified, and his testimony is true: and he knows that he speaks the truth, that you also may believe.

This is the disciple witnessing concerning these things, and having written the same: and we know that his testimony is true.