Gideon put the fleece out to prove to himself that God will keep his promises. Whether this was assurance or testing God, was probably a little bit of both. I believe he Gideon just had a few questions he needed answered as we all do at times and we all ask of God in times of need and God is willing to answer all our questions in his time, not ours. Gideons test was for reassurance and sometimes we test God to get what we want, like for example : a new car, house, clothes. Whatever. These aren't doing what God ask of us as Gideon was about to do for God.
God Is So Wonderful, that he Loves Us No Matter What and He will Forgive Us If We Just Ask Him.