The FactoryBot.register_strategy method is how to add a build strategy.

It takes two mandatory arguments: name and class. The name is a Symbol, and registering it exposes a method under FactoryBot::Syntax::Methods.

The class must define the methods association and result.

The association method takes an instance of FactoryRunner. You can #run this runner, passing a strategy name (it defaults to the current one) and an optional block. The block is called after the association is built, and is passed the object that was built.

The result method takes the object that was built for this factory (using initalize_with), and returns the result of this factory for this build strategy.