We all had times in our life when we did not do things according to God's plan. In general terms, we call this sin. The word sin actually means to miss the mark. By missing the mark, we are not pleasing God, we don't enhance our christian reputation.
Especially during our youth, we used to quote 1 Thessalonians 5:21 to aid us in times of weakness... Test all things. Hold on to the good. Yes, I agree, the verse is in the Bible. Unfortunately I've got a pet had in people using it. Miss-using it!
So, let us have a closer look. Take it in context. If we read some of the verses before it, all of it is encouragement. Uplifting. Don't pay back wrong for wrong. Be joyful always. Pray continually. Always give thanks. Avoid all evil. Don't put out the spirits fire.
All of the above are positives. All of it gives hope. Nothing is mentioned about sin. We must do it all: Test it all. Nowhere in the Bible is sin condoned. Not in 1 Thes 5:21 either. The aim is not to sin, never. Let's help each other. Lovingly...