If-None-Match → 304 (RFC 9110 §13.1.2)
"The origin server MUST respond with either a 304 (Not Modified) if the request method is GET or HEAD."
Send GET, capture ETag from response, then send conditional GET with If-None-Match: , expect 304. Tests conditional request compliance.
If-Modified-Since ignored when If-None-Match present (RFC 9110 §13.1.3)
"A recipient MUST ignore If-Modified-Since if the request contains an If-None-Match header field."
Send request with both If-None-Match (matching) and If-Modified-Since (distant past that would normally trigger 200). Should still return 304, proving IMS was ignored.
If-None-Match → 304 (RFC 9110 §13.1.2)
"The origin server MUST respond with either a 304 (Not Modified) if the request method is GET or HEAD."
Send GET, capture ETag from response, then send conditional GET with If-None-Match: , expect 304. Tests conditional request compliance.
If-Modified-Since ignored when If-None-Match present (RFC 9110 §13.1.3)
"A recipient MUST ignore If-Modified-Since if the request contains an If-None-Match header field."
Send request with both If-None-Match (matching) and If-Modified-Since (distant past that would normally trigger 200). Should still return 304, proving IMS was ignored.