text: from django.template import Context, Template
  from django.test import SimpleTestCase
  from django.utils import html
  from django.utils.functional import lazy, lazystr
  from django.utils.safestring import SafeData, mark_safe
  
  
  class customescape(str):
      def __html__(self):
          # implement specific and obviously wrong escaping
          # in order to be able to tell for sure when it runs
          return self.replace('<', '<<').replace('>', '>>')
  
  
  class SafeStringTest(SimpleTestCase):
      def assertRenderEqual(self, tpl, expected, **context):
          context = Context(context)
          tpl = Template(tpl)
          self.assertEqual(tpl.render(context), expected)
  
      def test_mark_safe(self):
          s = mark_safe('a&b')
  
          self.assertRenderEqual('{{ s }}', 'a&b', s=s)
          self.assertRenderEqual('{{ s|force_escape }}', 'a&amp;b', s=s)
  
      def test_mark_safe_str(self):
          """
          Calling str() on a SafeString instance doesn't lose the safe status.
          """
          s = mark_safe('a&b')
          self.assertIsInstance(str(s), type(s))
  
      def test_mark_safe_object_implementing_dunder_html(self):
          e = customescape('<a&b>')
          s = mark_safe(e)
          self.assertIs(s, e)
  
          self.assertRenderEqual('{{ s }}', '<<a&b>>', s=s)
          self.assertRenderEqual('{{ s|force_escape }}', '&lt;a&amp;b&gt;', s=s)
  
      def test_mark_safe_lazy(self):
          s = lazystr('a&b')
  
          self.assertIsInstance(mark_safe(s), SafeData)
          self.assertRenderEqual('{{ s }}', 'a&b', s=mark_safe(s))
  
      def test_mark_safe_object_implementing_dunder_str(self):
          class Obj:
              def __str__(self):
                  return '<obj>'
  
          s = mark_safe(Obj())
  
          self.assertRenderEqual('{{ s }}', '<obj>', s=s)
  
      def test_mark_safe_result_implements_dunder_html(self):
          self.assertEqual(mark_safe('a&b').__html__(), 'a&b')
  
      def test_mark_safe_lazy_result_implements_dunder_html(self):
          self.assertEqual(mark_safe(lazystr('a&b')).__html__(), 'a&b')
  
      def test_add_lazy_safe_text_and_safe_text(self):
          s = html.escape(lazystr('a'))
          s += mark_safe('&b')
          self.assertRenderEqual('{{ s }}', 'a&b', s=s)
  
          s = html.escapejs(lazystr('a'))
          s += mark_safe('&b')
          self.assertRenderEqual('{{ s }}', 'a&b', s=s)
  
      def test_mark_safe_as_decorator(self):
          """
          mark_safe used as a decorator leaves the result of a function
          unchanged.
          """
          def clean_string_provider():
              return '<html><body>dummy</body></html>'
  
          self.assertEqual(mark_safe(clean_string_provider)(), clean_string_provider())
  
      def test_mark_safe_decorator_does_not_affect_dunder_html(self):
          """
          mark_safe doesn't affect a callable that has an __html__() method.
          """
          class SafeStringContainer:
              def __html__(self):
                  return '<html></html>'
  
          self.assertIs(mark_safe(SafeStringContainer), SafeStringContainer)
  
      def test_mark_safe_decorator_does_not_affect_promises(self):
          """
          mark_safe doesn't affect lazy strings (Promise objects).
          """
          def html_str():
              return '<html></html>'
  
          lazy_str = lazy(html_str, str)()
          self.assertEqual(mark_safe(lazy_str), html_str())
  