Urls with name are not accessible in Django Client Tests (NoReverseMatch error)

I am writing tests for my views in django app. Previously they were in same directory in which my views are. They were working fine. But then I moved them in folder name 'tests' in django app. There are no import errors but I am getting 'NoReverseMatch' error. My directory structure is as follow.

Project
    settings.py
    |my_app
        |tests
            |tests.py
            |__init__.py
        |migrations
           |__init__.py
        |views.py
        |models.py
        |urls.py

My code is as follow

import os
os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'
import django
django.setup()
from rest_framework.reverse import reverse
from rest_framework import status
from rest_framework.test import APITestCase

class MyTests(APITestCase):

def test_01(self):
    url = reverse('login')
    data = {'username': 'username', 'password': 'StrongPassword'}
    response = self.client.post(url, data)
    self.assertEqual(response.data, my_expected_output)

The error which I am getting is

NoReverseMatch: Reverse for 'login' with arguments '()' and keyword arguments '{}' not found. 0 pattern(s) tried: []

Can anyone tell me where I am doing something wrong