Cannot authenticate with APIClient

tests.py

class AuthenticationTest(TestCase):
    def setUp(self):
        self.client = APIClient(enforce_csrf_checks=True)
        self.user_password = 'a12345678'
        self.user_username = 'admin'

        self.data = {
            'username': self.user_username,
            'password': self.user_password
        }

    def test_authenticating_jwt(self):
        """
        Given a username to authenticate,
        When user authenticates
        Then the DRF should return a JWT
        """

        # Not working
        response = self.client.post('/api-token-auth/', self.data, format='json')
        print response # Status 400 -- 'Unable to authenticate with provided credentials'
    
        # Works
        # response = requests.post('http://localhost:8080/api-token-auth/', self.data)
        # print response.content --> {'token': ...}
        

"Tests that require a database (namely, model tests) will not use your “real” (production) database. Separate, blank databases are created for the tests"

Refer to: https://docs.djangoproject.com/en/1.9/topics/testing/overview/#the-test-database

So when you are running the test for the user with username ''admin' and password 'a12345678', the user is not yet in your test database and thus you are unable to authenticate this user. So you should add the following in your setUp method

self.user = User.objects.create_user(self.user_username, self.user_password)
self.data = {
'username': self.username,
'password': self.password
}

It should work after this.