diff --git a/tests/test_main.py b/tests/test_main.py
index babe37d..6c2aa7d 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -40,7 +40,7 @@ def test_ultra_simple_failed():
 def test_ultra_simple_repr():
     m = UltraSimpleModel(a=10.2)
     assert repr(m) == '<UltraSimpleModel a=10.2 b=10>'
-    assert repr(m.fields['a']) == "<Field(a type=float required)>"
+    assert repr(m.fields['a']) == '<Field(a type=float required)>'
     assert dict(m) == {'a': 10.2, 'b': 10}
     assert m.dict() == {'a': 10.2, 'b': 10}
     assert m.json() == '{"a": 10.2, "b": 10}'
@@ -482,7 +482,7 @@ def test_arbitrary_type_allowed_validation_fails():
     assert exc_info.value.errors() == [
         {
             'loc': ('t',),
-            'msg': "instance of ArbitraryType expected",
+            'msg': 'instance of ArbitraryType expected',
             'type': 'type_error.arbitrary_type',
             'ctx': {'expected_arbitrary_type': 'ArbitraryType'},
         }
@@ -572,10 +572,10 @@ def test_dir_fields():
 
     m = MyModel(attribute_a=5)
 
-    assert "dict" in dir(m)
-    assert "json" in dir(m)
-    assert "attribute_a" in dir(m)
-    assert "attribute_b" in dir(m)
+    assert 'dict' in dir(m)
+    assert 'json' in dir(m)
+    assert 'attribute_a' in dir(m)
+    assert 'attribute_b' in dir(m)
 
 
 def test_dict_with_extra_keys():