TestCase assertions should work with TemplateResponse

[bmihelac]

When using assertContains for testing class based generic views or other views that returns TemplateResponse, following error is raised:

ContentNotRenderedError: The response content must be rendered before it can be accessed.

Example:

        response = SomeView.as_view()(request)
        self.assertContains(response, 'some content')

This can be avoided with adding response.render() before assertion is called, but in my opinion assertContain should check if content is rendered instead.

[mmcnickle]

Render TemplateReponse inside assertContains

[mmcnickle]

BLANK -- do not use

[mmcnickle]

I added a check if the response handed to assertContains is a TemplateResponse, and if so, will render it.
Added the same check to assertNotContains for consistency.

I do an explicit check for instanceof(response, SimpleTemplateResponse), but perhaps duck typing for any response with response.render() would be more appropriate/useful?

[Carl Meyer]

Replying to mmcnickle:

I do an explicit check for instanceof(response, SimpleTemplateResponse), but perhaps duck typing for any response with response.render() would be more appropriate/useful?

Yes, I think it'd be better to check for a callable response.render() rather than using isinstance. This (checking for the render method) is what Django already does in its normal response handling, after template response middleware.

[Julien Phalip]

In [17025]:

Fixed #15826 -- Made assertContains and assertNotContains work with SimpleTemplateResponse by forcing it to be rendered if it hasn't been rendered yet. Thanks to bmihelac for the report, to mmcnickle for the initial patch and tests, and to Carl Meyer for the guidance.