Class TestETag

tests/test_etag.py:16–105

Test our equal priority caching with ETags Equal Priority Caching is a term I've defined to describe when ETags are cached orthgonally from Time Based Caching.

class TestETag:
    """Test our equal priority caching with ETags

    Equal Priority Caching is a term I've defined to describe when
    ETags are cached orthgonally from Time Based Caching.
    """

    @pytest.fixture()
    def sess(self, url):
        self.etag_url = urljoin(url, "/etag")
        self.update_etag_url = urljoin(url, "/update_etag")
        self.cache = DictCache()
        sess = CacheControl(
            requests.Session(), cache=self.cache, serializer=NullSerializer()
        )
        yield sess

        # closing session object
        sess.close()

    def test_etags_get_example(self, sess, server):
        """RFC 2616 14.26

        The If-None-Match request-header field is used with a method to make
        it conditional. A client that has one or more entities previously
        obtained from the resource can verify that none of those entities
        is current by including a list of their associated entity tags in
        the If-None-Match header field. The purpose of this feature is to
        allow efficient updates of cached information with a minimum amount
        of transaction overhead

        If any of the entity tags match the entity tag of the entity that
        would have been returned in the response to a similar GET request
        (without the If-None-Match header) on that resource, [...] then
        the server MUST NOT perform the requested method, [...]. Instead, if
        the request method was GET or HEAD, the server SHOULD respond with
        a 304 (Not Modified) response, including the cache-related header
        fields (particularly ETag) of one of the entities that matched.

        (Paraphrased) A server may provide an ETag header on a response. On
        subsequent queries, the client may reference the value of this Etag
        header in an If-None-Match header; on receiving such a header, the
        server can check whether the entity at that URL has changed from the
        clients last version, and if not, it can return a 304 to indicate
        the client can use it's current representation.
        """
        r = sess.get(self.etag_url)

        # make sure we cached it
        assert self.cache.get(self.etag_url) == r.raw

        # make the same request
        resp = sess.get(self.etag_url)
        assert resp.raw == r.raw
        assert resp.from_cache

        # tell the server to change the etags of the response
        sess.get(self.update_etag_url)