Template html renderer tests (#4817)

tests/test_htmlrenderer.py

 from __future__ import unicode_literals
 
 import django.template.loader
+import pytest
 from django.conf.urls import url
-from django.core.exceptions import PermissionDenied
+from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.http import Http404
 from django.template import Template, TemplateDoesNotExist
 from django.test import TestCase, override_settings
@@ -46,6 +47,12 @@ urlpatterns = [
 @override_settings(ROOT_URLCONF='tests.test_htmlrenderer')
 class TemplateHTMLRendererTests(TestCase):
     def setUp(self):
+        class MockResponse(object):
+            template_name = None
+        self.mock_response = MockResponse()
+        self._monkey_patch_get_template()
+
+    def _monkey_patch_get_template(self):
         """
         Monkeypatch get_template
         """
@@ -87,6 +94,40 @@ class TemplateHTMLRendererTests(TestCase):
         self.assertEqual(response.content, six.b("403 Forbidden"))
         self.assertEqual(response['Content-Type'], 'text/html; charset=utf-8')
 
+    # 2 tests below are based on order of if statements in corresponding method
+    # of TemplateHTMLRenderer
+    def test_get_template_names_returns_own_template_name(self):
+        renderer = TemplateHTMLRenderer()
+        renderer.template_name = 'test_template'
+        template_name = renderer.get_template_names(self.mock_response, view={})
+        assert template_name == ['test_template']
+
+    def test_get_template_names_returns_view_template_name(self):
+        renderer = TemplateHTMLRenderer()
+
+        class MockResponse(object):
+            template_name = None
+
+        class MockView(object):
+            def get_template_names(self):
+                return ['template from get_template_names method']
+
+        class MockView2(object):
+            template_name = 'template from template_name attribute'
+
+        template_name = renderer.get_template_names(self.mock_response,
+                                                    MockView())
+        assert template_name == ['template from get_template_names method']
+
+        template_name = renderer.get_template_names(self.mock_response,
+                                                    MockView2())
+        assert template_name == ['template from template_name attribute']
+
+    def test_get_template_names_raises_error_if_no_template_found(self):
+        renderer = TemplateHTMLRenderer()
+        with pytest.raises(ImproperlyConfigured):
+            renderer.get_template_names(self.mock_response, view=object())
+
 
 @override_settings(ROOT_URLCONF='tests.test_htmlrenderer')
 class TemplateHTMLRendererExceptionTests(TestCase):