Python "responses library: no match for registered URL" in CI

The responses library raises a ConnectionError when code makes an HTTP request that does not match any registered mock. The message lists the unmatched request and the registered responses so you can see the mismatch.

What this error means

A test fails with "requests.exceptions.ConnectionError: Connection refused by Responses - the call doesn't match any registered mock" and a diff of requested vs registered URLs.

pytest

ConnectionError: Connection refused by Responses - the call doesn't match any registered mock.

Request: - GET https://api.example.com/v2/items
Registered responses: - GET https://api.example.com/v1/items

Common causes

No mock registered for the exact URL/method

The code calls a URL (or method, or query string) that no registered response matches.

A path, query, or body matcher mismatch

A registered response targets a slightly different path or requires a matcher the request does not satisfy.

How to fix it

Register a matching response or relax the matcher

Register a response for the exact method and URL the code calls.
Use match parameters (query string, body) only when needed, and align them with the request.
Enable assert_all_requests_are_fired to catch unused/missing mocks.

Python

import responses

@responses.activate
def test_items():
    responses.add(responses.GET, "https://api.example.com/v2/items", json=[], status=200)
    ...

How to prevent it

Register mocks for every endpoint the code under test calls.
Keep mock URLs in sync with the client code.
Use assert_all_requests_are_fired to find drift.