How would you get a DNA test done on a baby that you think is yours but the mother refuses to get the baby tested and keeps saying that the baby is not yours?

As the birth mother she has every right to refuse you. Why can't you take her word that the baby is not yours. Many men would be happy to avoid responsibility and not have to pay child support.

You file with your local Family Court (or the branch of the Court that handles custody and support matters) and file a Petition requesting visitation. The Court will ORDER paternity testing and the mother will have no choice in the matter.

Please pay more attention to posting guidelines. There is a Read First sticky in many forums that directs questions of a legal nature to this forum.

As noted, the mother does not have to VOLUNTARILY submit to a DNA test. Also, any test that is NOT court ordered will generally have no weight in court. So your only recourse is the court system. You file for joint legal custody and visitation in your local courts. The court will then order a paternity test before ruling.