How to test new Django 1.10+ MIDDLEWARE classes

I'm upgrading existing middleware to a new style 1.10+ Django middleware.

Previously it was one similar to this:

class ThreadLocalMiddleware(MiddlewareMixin):
    """ Simple middleware that adds the request object in thread local storage."""
    def process_request(self, request):
        _thread_locals.request = request

    def process_response(self, request, response):
        if hasattr(_thread_locals, 'request'):
            del _thread_locals.request
        return response

    def process_exception(self, request, exception):
        if hasattr(_thread_locals, 'request'):
            del _thread_locals.request

after rewrite to the new style:

class ThreadLocalMiddleware:
    def __init__(self, get_response=None):
        self.get_response = get_response

    def __call__(self, request):
        _thread_locals.request = request

        response = self.get_response(request)

        if hasattr(_thread_locals, 'request'):
            del _thread_locals.request
        return response

    def process_exception(self, request, exception):
        if hasattr(_thread_locals, 'request'):
            del _thread_locals.request

My question is how to test that the middleware sets the request in the _thread_locals? Previously it was as easy as calling the process_request method in tests. Now I have only the call which will erase the variable at the end.