Tests to validate field inputs such as

test_field_posts.py

from django.test import TestCase
from rest_framework.test import APIClient
from authorsHaven.models import Post
  
class PostTest(TestCase):
  """ This is to test that the Post created has author, title, text in field, create and publish dates """
  def setUp(self):
        # Setup run before every test method.
        pass
  posts= {
  'author.self'='Andrew Hicks',
  'title.self':'The Dry Lands',
  'text.self'='',
  'created_date.self' = '14/12/2018',
  'published_date.self'= '18/12/2018',
  }
      
  def test_author_field(self):
    self.assertEqual(author, 'Andrew Hicks')
    
   def test_tile_field(self):
    self.assertEqual(title, 'The Dry Lands')
    
   def test_text_field(self):
    self.assertNotEqual(text, '')
    
   def test_created_date_field(self):
    self.assertEqual(created_date, '14/12/2018')
    
   def test_published_date_field(self):
    self.assertEqual(published_date, '18/12/2018')
    
   def tearDown(self):
        # Clean up run after every test method.
        pass

In your setUp method, get rid of the pass and also ensure your posts variable is a class variable.

self.posts = {}

add a blank line between the libraries' imports and local application imports to help easily demarcate the different imports.
Ensure that the pep8 standards are followed as you are writing the code.

from authorsHaven.models import Post

The Post model seems not to have been used, consider removing that import statement

Good work. However, check your setUp and tearDown methods and ensure they adhere to PEP 8 standards by de-indenting the contents within it by a single tab or four spaces.