All branches of Buddhism fall under Mahayana and Theravada. There is no third vehicle (yana). To be a Theravada practitioner, the first requisite is having unshakable renunciation—complete distaste for worldly fulfillments and whole-hearted pursuit of liberation from samsara. Do we have such resolution? If not, we would not qualify as Theravada practitioners.
Mahayana practitioners, on the other hand, must have undaunted bodhicitta and be willing to serve the needs of others unselfishly and unconditionally. Can we do that? If not, we would not be deemed Mahayana practitioners either.
Depicted from Luminous Wisdom Book Series : The Three Supreme Methods