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Fix MockTransport not setting elapsed property #3757

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Fix MockTransport not setting elapsed property #3757

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50c162c
Fix MockTransport not setting elapsed property
veeceey Feb 8, 2026
324e16a
Fix code formatting in test_client.py
veeceey Feb 8, 2026
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3 changes: 3 additions & 0 deletions httpx/_transports/mock.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
from __future__ import annotations

import datetime
import typing

from .._models import Request, Response
Expand All @@ -24,6 +25,7 @@ def handle_request(
response = self.handler(request)
if not isinstance(response, Response): # pragma: no cover
raise TypeError("Cannot use an async handler in a sync Client")
response.elapsed = datetime.timedelta()

@jeonjw85 jeonjw85 Oct 15, 2026

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[P2] Preserve elapsed values explicitly supplied by the mock handler

This unconditionally replaces timing metadata that the handler already supplied, rather than just defaulting a missing value:

def handler(request):
    response = httpx.Response(200, text="ok")
    response.elapsed = timedelta(seconds=7)
    return response

with httpx.Client(transport=httpx.MockTransport(handler)) as client:
    assert client.get("http://local.invalid/").elapsed == timedelta(seconds=7)

The assertion passes on the base but fails here because elapsed becomes zero. This breaks existing mocks that deliberately simulate response timings, including the explicit assignment shown in #3712. The async assignment has the same regression. Please preserve a supplied elapsed value when adding the default.

Automated review; reproduced through both Client and AsyncClient on Python 3.13.15, base b5addb6 versus head 324e16a.

return response

async def handle_async_request(
Expand All @@ -40,4 +42,5 @@ async def handle_async_request(
if not isinstance(response, Response):
response = await response

response.elapsed = datetime.timedelta()
return response
39 changes: 39 additions & 0 deletions tests/client/test_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -460,3 +460,42 @@ def cp1252_but_no_content_type(request):
assert response.reason_phrase == "OK"
assert response.encoding == "ISO-8859-1"
assert response.text == text


def test_mock_transport_elapsed():
"""Test that MockTransport sets the elapsed property.

Regression test for https://github.com/encode/httpx/issues/3712
"""

def handler(request):
return httpx.Response(200, json={"text": "Hello, world!"})

transport = httpx.MockTransport(handler)
with httpx.Client(transport=transport) as client:
response = client.get("http://www.example.com")
assert response.status_code == 200
# MockTransport should set elapsed to timedelta(0)
assert response.elapsed == timedelta(0)
# Accessing elapsed should not raise RuntimeError
assert isinstance(response.elapsed, timedelta)


@pytest.mark.anyio
async def test_async_mock_transport_elapsed():
"""Test that MockTransport sets the elapsed property for async requests.

Regression test for https://github.com/encode/httpx/issues/3712
"""

def handler(request):
return httpx.Response(200, json={"text": "Hello, world!"})

transport = httpx.MockTransport(handler)
async with httpx.AsyncClient(transport=transport) as client:
response = await client.get("http://www.example.com")
assert response.status_code == 200
# MockTransport should set elapsed to timedelta(0)
assert response.elapsed == timedelta(0)
# Accessing elapsed should not raise RuntimeError
assert isinstance(response.elapsed, timedelta)