def METHOD_NAME(self):
    """
    Test replacing Null mbi_hash value in crosswalk.
    Unlike hich_hash, this case is OK if past value was Null/None.
    """
    user = self._create_user(
        "john",
        "password",
        first_name="John",
        last_name="Smith",
        email="john@smith.net",
        user_mbi_hash=None,
    )
    cw = Crosswalk.objects.get(user=user)
    self.assertEqual(cw.user_mbi_hash, None)
    cw.user_mbi_hash = (
        "239e178537ed3bc486e6a7195a47a82a2cd6f46e911660fe9775f6e0dd3f1130"
    )
    cw.save()
    cw = Crosswalk.objects.get(user=user)
    self.assertEqual(
        cw.user_mbi_hash,
        "239e178537ed3bc486e6a7195a47a82a2cd6f46e911660fe9775f6e0dd3f1130",
    )