diff --git a/django/db/backends/postgresql/creation.py b/django/db/backends/postgresql/creation.py
index a609f33fd6..eb8ac3bcf5 100644
--- a/django/db/backends/postgresql/creation.py
+++ b/django/db/backends/postgresql/creation.py
@@ -2,6 +2,7 @@ import sys
 
 from psycopg2 import errorcodes
 
+from django.core.exceptions import ImproperlyConfigured
 from django.db.backends.base.creation import BaseDatabaseCreation
 from django.db.backends.utils import strip_quotes
 
@@ -21,9 +22,11 @@ class DatabaseCreation(BaseDatabaseCreation):
 
     def sql_table_creation_suffix(self):
         test_settings = self.connection.settings_dict['TEST']
-        assert test_settings['COLLATION'] is None, (
-            "PostgreSQL does not support collation setting at database creation time."
-        )
+        if test_settings.get('COLLATION') is not None:
+            raise ImproperlyConfigured(
+                'PostgreSQL does not support collation setting at database '
+                'creation time.'
+            )
         return self._get_database_create_suffix(
             encoding=test_settings['CHARSET'],
             template=test_settings.get('TEMPLATE'),
diff --git a/django/test/testcases.py b/django/test/testcases.py
index b2720c50f3..b947d70a45 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -1253,7 +1253,8 @@ class TestCase(TransactionTestCase):
             self.setUpTestData()
             return super()._fixture_setup()
 
-        assert not self.reset_sequences, 'reset_sequences cannot be used on TestCase instances'
+        if self.reset_sequences:
+            raise TypeError('reset_sequences cannot be used on TestCase instances')
         self.atomics = self._enter_atomics()
 
     def _fixture_teardown(self):
diff --git a/tests/backends/postgresql/test_creation.py b/tests/backends/postgresql/test_creation.py
index 20f5f7ede9..eb68c6e471 100644
--- a/tests/backends/postgresql/test_creation.py
+++ b/tests/backends/postgresql/test_creation.py
@@ -3,6 +3,7 @@ from contextlib import contextmanager
 from io import StringIO
 from unittest import mock
 
+from django.core.exceptions import ImproperlyConfigured
 from django.db import DatabaseError, connection
 from django.db.backends.base.creation import BaseDatabaseCreation
 from django.test import SimpleTestCase
@@ -61,6 +62,15 @@ class DatabaseCreationTests(SimpleTestCase):
         settings = {'CHARSET': 'UTF8', 'TEMPLATE': 'template0'}
         self.check_sql_table_creation_suffix(settings, '''WITH ENCODING 'UTF8' TEMPLATE "template0"''')
 
+    def test_sql_table_creation_raises_with_collation(self):
+        settings = {'COLLATION': 'test'}
+        msg = (
+            'PostgreSQL does not support collation setting at database '
+            'creation time.'
+        )
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            self.check_sql_table_creation_suffix(settings, None)
+
     def _execute_raise_database_already_exists(self, cursor, parameters, keepdb=False):
         error = DatabaseError('database %s already exists' % parameters['dbname'])
         error.pgcode = errorcodes.DUPLICATE_DATABASE
diff --git a/tests/test_utils/test_testcase.py b/tests/test_utils/test_testcase.py
index 5ec71f84d0..9b11168b13 100644
--- a/tests/test_utils/test_testcase.py
+++ b/tests/test_utils/test_testcase.py
@@ -43,6 +43,16 @@ class TestTestCase(TestCase):
         with self.assertRaisesMessage(AssertionError, message):
             Car.objects.using('other').get()
 
+    def test_reset_sequences(self):
+        old_reset_sequences = self.reset_sequences
+        self.reset_sequences = True
+        msg = 'reset_sequences cannot be used on TestCase instances'
+        try:
+            with self.assertRaisesMessage(TypeError, msg):
+                self._fixture_setup()
+        finally:
+            self.reset_sequences = old_reset_sequences
+
 
 class NonDeepCopyAble:
     def __deepcopy__(self, memo):