diff --git a/tests/utils_tests/test_encoding.py b/tests/utils_tests/test_encoding.py
index 1f5d5891ac..bca6549fe7 100644
--- a/tests/utils_tests/test_encoding.py
+++ b/tests/utils_tests/test_encoding.py
@@ -1,13 +1,16 @@
 import datetime
 import unittest
+from unittest import mock
 from urllib.parse import quote_plus
 
 from django.test import SimpleTestCase
 from django.utils.encoding import (
     DjangoUnicodeDecodeError, escape_uri_path, filepath_to_uri, force_bytes,
-    force_text, iri_to_uri, smart_text, uri_to_iri,
+    force_text, get_system_encoding, iri_to_uri, smart_bytes, smart_text,
+    uri_to_iri,
 )
 from django.utils.functional import SimpleLazyObject
+from django.utils.translation import gettext_lazy
 
 
 class TestEncodingUtils(SimpleTestCase):
@@ -49,27 +52,45 @@ class TestEncodingUtils(SimpleTestCase):
         today = datetime.date.today()
         self.assertEqual(force_bytes(today, strings_only=True), today)
 
+    def test_force_bytes_encoding(self):
+        error_msg = 'This is an exception, voilà'.encode()
+        result = force_bytes(error_msg, encoding='ascii', errors='ignore')
+        self.assertEqual(result, b'This is an exception, voil')
+
+    def test_force_bytes_memory_view(self):
+        self.assertEqual(force_bytes(memoryview(b'abc')), b'abc')
+
+    def test_smart_bytes(self):
+        class Test:
+            def __str__(self):
+                return 'ŠĐĆŽćžšđ'
+
+        lazy_func = gettext_lazy('x')
+        self.assertIs(smart_bytes(lazy_func), lazy_func)
+        self.assertEqual(smart_bytes(Test()), b'\xc5\xa0\xc4\x90\xc4\x86\xc5\xbd\xc4\x87\xc5\xbe\xc5\xa1\xc4\x91')
+        self.assertEqual(smart_bytes(1), b'1')
+        self.assertEqual(smart_bytes('foo'), b'foo')
+
     def test_smart_text(self):
         class Test:
             def __str__(self):
                 return 'ŠĐĆŽćžšđ'
 
-        class TestU:
-            def __str__(self):
-                return 'ŠĐĆŽćžšđ'
-
-            def __bytes__(self):
-                return b'Foo'
-
+        lazy_func = gettext_lazy('x')
+        self.assertIs(smart_text(lazy_func), lazy_func)
         self.assertEqual(smart_text(Test()), '\u0160\u0110\u0106\u017d\u0107\u017e\u0161\u0111')
-        self.assertEqual(smart_text(TestU()), '\u0160\u0110\u0106\u017d\u0107\u017e\u0161\u0111')
         self.assertEqual(smart_text(1), '1')
         self.assertEqual(smart_text('foo'), 'foo')
 
+    def test_get_default_encoding(self):
+        with mock.patch('locale.getdefaultlocale', side_effect=Exception):
+            self.assertEqual(get_system_encoding(), 'ascii')
+
 
 class TestRFC3987IEncodingUtils(unittest.TestCase):
 
     def test_filepath_to_uri(self):
+        self.assertEqual(filepath_to_uri(None), None)
         self.assertEqual(filepath_to_uri('upload\\чубака.mp4'), 'upload/%D1%87%D1%83%D0%B1%D0%B0%D0%BA%D0%B0.mp4')
 
     def test_iri_to_uri(self):
@@ -82,6 +103,7 @@ class TestRFC3987IEncodingUtils(unittest.TestCase):
             # Reserved chars remain unescaped.
             ('%&', '%&'),
             ('red&♥ros%#red', 'red&%E2%99%A5ros%#red'),
+            (gettext_lazy('red&♥ros%#red'), 'red&%E2%99%A5ros%#red'),
         ]
 
         for iri, uri in cases:
@@ -92,6 +114,7 @@ class TestRFC3987IEncodingUtils(unittest.TestCase):
 
     def test_uri_to_iri(self):
         cases = [
+            (None, None),
             # Valid UTF-8 sequences are decoded.
             ('/%e2%89%Ab%E2%99%a5%E2%89%aB/', '/≫♥≫/'),
             ('/%E2%99%A5%E2%99%A5/?utf8=%E2%9C%93', '/♥♥/?utf8=✓'),