diff --git a/tests/unit/containers/__init__.py b/tests/unit/containers/__init__.py
index 69cef935..bfcb6292 100644
--- a/tests/unit/containers/__init__.py
+++ b/tests/unit/containers/__init__.py
@@ -1 +1 @@
-"""Dependency injector container unit tests."""
+"""Container tests."""
diff --git a/tests/unit/containers/cls/test_custom_strings_py2_py3.py b/tests/unit/containers/cls/test_custom_strings_py2_py3.py
new file mode 100644
index 00000000..940a41f3
--- /dev/null
+++ b/tests/unit/containers/cls/test_custom_strings_py2_py3.py
@@ -0,0 +1,36 @@
+"""Tests for container cls with custom string classes as attribute names.
+
+See: https://github.com/ets-labs/python-dependency-injector/issues/479
+"""
+
+from dependency_injector import containers, providers
+from pytest import fixture, raises
+
+
+class CustomString(str):
+    pass
+
+
+class CustomClass:
+    thing = None
+
+
+class Container(containers.DeclarativeContainer):
+    pass
+
+
+@fixture
+def provider():
+    return providers.Provider()
+
+
+def test_setattr(provider):
+    setattr(Container, CustomString("test_attr"), provider)
+    assert Container.test_attr is provider
+
+
+def test_delattr():
+    setattr(Container, CustomString("test_attr"), provider)
+    delattr(Container, CustomString("test_attr"))
+    with raises(AttributeError):
+        Container.test_attr
diff --git a/tests/unit/containers/test_declarative_py2_py3.py b/tests/unit/containers/test_declarative_py2_py3.py
deleted file mode 100644
index ac774e3f..00000000
--- a/tests/unit/containers/test_declarative_py2_py3.py
+++ /dev/null
@@ -1,35 +0,0 @@
-"""Dependency injector declarative container unit tests."""
-
-import unittest
-
-from dependency_injector import (
-    containers,
-    providers,
-)
-
-
-class DeclarativeContainerWithCustomStringTests(unittest.TestCase):
-    # See: https://github.com/ets-labs/python-dependency-injector/issues/479
-
-    class CustomString(str):
-        pass
-
-    class CustomClass:
-        thing = None
-
-    class CustomContainer(containers.DeclarativeContainer):
-        pass
-
-    def setUp(self):
-        self.container = self.CustomContainer
-        self.provider = providers.Provider()
-
-    def test_setattr(self):
-        setattr(self.container, self.CustomString("test_attr"), self.provider)
-        self.assertIs(self.container.test_attr, self.provider)
-
-    def test_delattr(self):
-        setattr(self.container, self.CustomString("test_attr"), self.provider)
-        delattr(self.container, self.CustomString("test_attr"))
-        with self.assertRaises(AttributeError):
-            self.container.test_attr