test_auth.py

from django.test import TestCase
from rest_framework import status
from rest_framework.test import APIClient

class LoginTestCase(TestCase):
  
  def setUp(self):
    self.client = APIClient()
    self.user = {
      'username':'allanimire',
      'password':'password123'
    }
    self.non_user = {
      'username':'',
      'password':'password123'
    }
    
   def test_successfull_login(self):
    resp = self.client.post('api/users', self.user, format='json')
    self.assertIn(b'User successfully logged in', resp.data)
    
   def test_unsucessfull_login(self):
    resp = self.client.post('api/users', self.non_user, format='json')
    self.assertTrue(resp.status_code, status.HTTP_400_BAD_REQUEST)
    
  

Your tests are straight to the point. The unsuccessful scenario would be better with more tests. Like:

It is good that the tests are straight to the point. As @gitaumoses4 mentioned, test_unsucessful should have more scenarios.