Add Selector provider tests

tests/unit/providers/test_traversal_py3.py

@@ -671,3 +671,59 @@ class ContainerTests(unittest.TestCase):
         )
         self.assertIn(provider.last_overriding, all_providers)
         self.assertIs(provider.last_overriding(), container2)
+
+
+class SelectorTests(unittest.TestCase):
+
+    def test_traverse(self):
+        switch = lambda: 'provider1'
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+
+        provider = providers.Selector(
+            switch,
+            provider1=provider1,
+            provider2=provider2,
+        )
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_switch(self):
+        switch = providers.Callable(lambda: 'provider1')
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+
+        provider = providers.Selector(
+            switch,
+            provider1=provider1,
+            provider2=provider2,
+        )
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(switch, all_providers)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+        selector1 = providers.Selector(lambda: 'provider1', provider1=provider1)
+
+        provider = providers.Selector(
+            lambda: 'provider2',
+            provider2=provider2,
+        )
+        provider.override(selector1)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(selector1, all_providers)