title: How to test related models in Django v3
body: <p>I am trying to test <code>Destination</code> and <code>Comment</code> models and check if they are related in the test.</p>
  <p>I have already tested the <code>Destinations</code> models and it pass the test with the approach:</p>
  <pre><code>def test_destinations_model(self):
          destination = Destinations.objects.create(
              tour_title = 'test1',
              booking_start_date='2021-05-30',
              booking_end_date= '2022-05-30',
              price=2000,
              description='test1',
              author='test1',
              image='image.png'
          )
          destination.save()
          self.assertEquals(destination.tour_title, 'test1')
          self.assertEquals(destination.booking_start_date, '2021-05-30')
          self.assertEquals(destination.booking_end_date, '2022-05-30')
          self.assertEquals(destination.price, 2000)
          self.assertEquals(destination.description, 'test1')
          self.assertEquals(destination.author, 'test1')
          self.assertEquals(destination.image, 'image.png')
  </code></pre>
  <p>However, I don't know how to test the <code>Comment</code> model since it is related to the <code>Destinations</code> one. I have done the following approach but the test is failing with the following message:</p>
  <pre><code>#message of failing test for test_comment_model 
  
  self.assertEquals(destination, comment)
  AssertionError: &lt;Destinations: test1&gt; != &lt;Comment: Comment test1 by John&gt;
  </code></pre>
  <pre><code>
  #Failling test:
  def test_comment_model(self):
          #post not needed to test as foreignKey
          destination = Destinations(
              tour_title = 'test1',
              booking_start_date='2021-05-30',
              booking_end_date= '2022-05-30',
              price=2000,
              description='test1',
              author='test1',
              image='image.png'
          )
          destination.save()
          comment = Comment(
              post=destination,
              name = 'John',
              email = 'any@email.com',
              comment = 'test1',
              created_on = timezone.now(),
              active = False,
  
          )
          comment.save()
          self.assertEquals(destination, comment)
  
  
  </code></pre>
  <pre><code>class Destinations(models.Model):
  
      author = models.CharField(max_length=200, unique=False)
      tour_title = models.CharField(max_length=250)
      description = RichTextUploadingField()
      image = models.ImageField(upload_to='tour_images', blank=True)
      location = models.CharField(max_length=250)
      booking_start_date = models.DateField()
      booking_end_date = models.DateField()
      price = models.DecimalField(max_digits=6, decimal_places=2)
  
      def __str__(self):
          return self.tour_title
  </code></pre>
  <pre><code>
  class Comment(models.Model):
      post = models.ForeignKey(Destinations,on_delete=models.CASCADE,related_name='comments')
      name = models.CharField(max_length=80)
      email = models.EmailField()
      comment = models.TextField()
      created_on = models.DateTimeField(auto_now_add=True)
      active = models.BooleanField(default=False)
  
      class Meta:
          ordering = ['created_on']
  
      def __str__(self):
          return 'Comment {} by {}'.format(self.comment, self.name)
  </code></pre>