For a Christian, your testimony of salvation is your personal story. It's called a testimony because we get to testify about how God saved us, by His GRACE.
Even though each of our individual past circumstances and lifestyles are different, the stories we tell all point to the wonderful Cross-work of Christ and how He SAVED our SOUL!
When a non-Christian hears our testimony, they may laugh it off as some sort of fairy-tail story.
This is ironic because most Americans have been brought on fairy-tail stories. Most parents raise their kids, reading them books about Cinderella, Snow White, Beauty and the Beast, The Little Mermaid, Goldilocks and the 3 Bears, Little Red Riding Hood, Santa Claus, the Easter Bunny and Cupid!
If a lost person claims that your testimony is a fairy tale story, gently remind them that they've based their entire life living for and following after fairy tales.
Remind them that your TESTIMONY is the true, honest account of the glorious Gospel of God and what He did to save your soul from sin.
Remind them that the gift of salvation is freely offered and is available to them to receive.
Finally, remember that this world works overtime to train and educate people to believe a lie. They push them to read every book out there except the true History Book of the Bible!
The solution is:
Tell YOUR story!
Give YOUR testimony!
Preach the GOSPEL!
Romans 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth;