def METHOD_NAME(self):
    """Test overwriting the register length."""
    op = FermionicOp({"+_0 -_0": 1}, num_spin_orbitals=1)
    expected = FermionicOp({"+_0 -_0": 1}, num_spin_orbitals=3)
    mapper = JordanWignerMapper()
    self.assertEqual(mapper.map(op, register_length=3), mapper.map(expected))