The whole revelation of God, testifying to man what he is to believe, do, and hope, Psalms 19:7 119:88,99 1 Corinthians 1:6 Revelation 1:2. The two stone tables of the law were a visible "testimony" or witness of God’s covenant with his people; and hence the ark of the covenant was called sometimes the testimony, or the ark of the testimony, Exodus 25:22 34:29. See ARK.
These dictionary topics are from American Tract Society Bible Dictionary published in 1859. Public Domain, copy freely.
Rand, W. W. "Entry for 'TESTIMONY'". "American Tract Society Bible Dictionary".