It is important for children to know who their parents are. It's also important for parents - particularly fathers - to take responsibility for the children they produce. This means paying child support and being involved in their children's lives. Paternity testing is a common way for the courts to determine if a man is the father of a child. For those who do want to assume paternity of a child, there are ways to do so through the state of Washington without having to submit to a genetic test.
When a couple is married at the time their child is born, the man is considered to be the father unless either parent or another party challenges that assumption. No special paperwork is required to validate this claim. The same applies when a couple is in a registered domestic partnership - which is recognized in Washington - throughout the pregnancy. The man is presumed to be the father unless there is any disagreement.