The Bible tells us that we will know a lot about a person by the fruit that is produced in their life. And Jesus told his disciples how they can bear the right kid of fruit through the true vine, himself. The evidence of our saving faith will be in the fruit that is produced as we abide on the vine, Jesus Christ, and as we are pruned by the vinedresser, our Heavenly Father.
"I am the vine; you are the branches. Whoever abides in me and I in him, he it is that bears much fruit, for apart from me you can do nothing." John 15:5