diff --git a/docs/guide/mongomock.rst b/docs/guide/mongomock.rst
index d70ee6a6..040ff912 100644
--- a/docs/guide/mongomock.rst
+++ b/docs/guide/mongomock.rst
@@ -2,10 +2,10 @@
 Use mongomock for testing
 ==============================
 
-`mongomock <https://github.com/vmalloc/mongomock/>`_ is a package to do just 
+`mongomock <https://github.com/vmalloc/mongomock/>`_ is a package to do just
 what the name implies, mocking a mongo database.
 
-To use with mongoengine, simply specify mongomock when connecting with 
+To use with mongoengine, simply specify mongomock when connecting with
 mongoengine:
 
 .. code-block:: python
@@ -45,4 +45,4 @@ Example of test file:
             pers.save()
 
             fresh_pers = Person.objects().first()
-            self.assertEqual(fresh_pers.name, 'John')
+            assert fresh_pers.name ==  'John'
diff --git a/tests/document/test_instance.py b/tests/document/test_instance.py
index b899684f..609d0690 100644
--- a/tests/document/test_instance.py
+++ b/tests/document/test_instance.py
@@ -3338,19 +3338,19 @@ class TestInstance(MongoDBTestCase):
 
         # worker1.job should be equal to the job used originally to create the
         # document.
-        self.assertEqual(worker1.job, worker.job)
+        assert worker1.job == worker.job
 
         # worker1.job should be equal to a newly created Job EmbeddedDocument
         # using either the Boss object or his ID.
-        self.assertEqual(worker1.job, Job(boss=boss, boss_dbref=boss))
-        self.assertEqual(worker1.job, Job(boss=boss.id, boss_dbref=boss.id))
+        assert worker1.job == Job(boss=boss, boss_dbref=boss)
+        assert worker1.job == Job(boss=boss.id, boss_dbref=boss.id)
 
         # The above equalities should also hold after worker1.job.boss has been
         # fetch()ed.
         worker1.job.boss.fetch()
-        self.assertEqual(worker1.job, worker.job)
-        self.assertEqual(worker1.job, Job(boss=boss, boss_dbref=boss))
-        self.assertEqual(worker1.job, Job(boss=boss.id, boss_dbref=boss.id))
+        assert worker1.job == worker.job
+        assert worker1.job == Job(boss=boss, boss_dbref=boss)
+        assert worker1.job == Job(boss=boss.id, boss_dbref=boss.id)
 
     def test_dbref_equality(self):
         class Test2(Document):
@@ -3693,13 +3693,13 @@ class TestInstance(MongoDBTestCase):
         value = u"I_should_be_a_dict"
         coll.insert_one({"light_saber": value})
 
-        with self.assertRaises(InvalidDocumentError) as cm:
+        with pytest.raises(InvalidDocumentError) as exc_info:
             list(Jedi.objects)
 
-        self.assertEqual(
-            str(cm.exception),
-            "Invalid data to create a `Jedi` instance.\nField 'light_saber' - The source SON object needs to be of type 'dict' but a '%s' was found"
-            % type(value),
+        assert str(
+            exc_info.value
+        ) == "Invalid data to create a `Jedi` instance.\nField 'light_saber' - The source SON object needs to be of type 'dict' but a '%s' was found" % type(
+            value
         )
 
 
diff --git a/tests/fields/test_file_field.py b/tests/fields/test_file_field.py
index bfc86511..b8ece1a9 100644
--- a/tests/fields/test_file_field.py
+++ b/tests/fields/test_file_field.py
@@ -151,7 +151,7 @@ class TestFileField(MongoDBTestCase):
         result = StreamFile.objects.first()
         assert streamfile == result
         assert result.the_file.read() == text + more_text
-        # self.assertEqual(result.the_file.content_type, content_type)
+        # assert result.the_file.content_type == content_type
         result.the_file.seek(0)
         assert result.the_file.tell() == 0
         assert result.the_file.read(len(text)) == text