pytest-mqtt

About

pytest-mqtt supports testing systems based on MQTT by providing test fixtures for pytest. It has been conceived for the fine terkin-datalogger and mqttwarn programs.

capmqtt fixture

Capture MQTT messages, using the Paho MQTT Python Client, in the spirit of caplog and capsys. It can also be used to publish MQTT messages.

MQTT server host and port are configurable via pytest cli arguments: --mqtt-host and --mqtt-port. Default values are localhost/1883.

You may additionally specify a username and password for connecting to the broker with: --mqtt-username and --mqtt-password. Default values are guest/guest.

By default, the test fixture subscribes to all topics, listening on #. This can be disabled with the --no-subscribe-all option. You can then subscribe to the topics you are interested in within each test using capmqtt.mqtt_client.client.subscribe(cpe.info).

mosquitto fixture

Provide the Mosquitto MQTT broker as a session-scoped fixture to your test cases.

Usage

import pytest
from pytest_mqtt.model import MqttMessage

@pytest.mark.capmqtt_decode_utf8
def test_mqtt_send_receive(mosquitto, capmqtt):
    """
    Basic send/receive roundtrip, using text payload (`str`).

    By using the `capmqtt_decode_utf8` marker, the message payloads
    will be recorded as `str`, after decoding them from `utf-8`.
    Otherwise, message payloads would be recorded as `bytes`.
    """

    # Submit a basic MQTT message.
    capmqtt.publish(topic="foo", payload="bar")

    # Demonstrate the "messages" property.
    # It returns a list of "MqttMessage" objects.
    assert capmqtt.messages == [
        MqttMessage(topic="foo", payload="bar", userdata=None),
    ]

    # Demonstrate the "records" property.
    # It returns tuples of "(topic, payload, userdata)".
    assert capmqtt.records == [
        ("foo", "bar", None),
    ]

The capmqtt_decode_utf8 setting can be enabled in three ways.

Session-wide, per pytestconfig option, for example within conftest.py:

@pytest.fixture(scope="session", autouse=True)
def configure_capmqtt_decode_utf8(pytestconfig):
    pytestconfig.option.capmqtt_decode_utf8 = True

On the module level, just say capmqtt_decode_utf8 = True on top of your file.
On individual test cases as a test case marker, using @pytest.mark.capmqtt_decode_utf8.

Issues

The mosquitto fixture currently does not support either authentication or encryption.
capmqtt should be able to capture messages only from specified topics.

Development

git clone https://github.com/mqtt-tools/pytest-mqtt
cd pytest-mqtt
python3 -m venv .venv
source .venv/bin/activate
pip install --editable=.[test,develop]
poe test

Project information

Contributions

Every kind of contribution, feedback, or patch, is much welcome. Create an issue or submit a patch if you think we should include a new feature, or to report or fix a bug.

Resources

License

The project is licensed under the terms of the MIT license, see LICENSE.

Release files for pytest-mqtt 0.7.0

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for pytest-mqtt 0.7.0
File	Size	Uploaded
pytest_mqtt-0.7.0.tar.gz	11.8 kB	Jan 28, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for pytest-mqtt 0.7.0
File	Interpreter	ABI	Platform	Reset
pytest_mqtt-0.7.0-py3-none-any.whl 10.2 kB Jan 28, 2026	Python 3	none	any	Details

Total release size: 22.0 kB

Release files / pytest_mqtt-0.7.0.tar.gz

Download URL	pytest_mqtt-0.7.0.tar.gz
Size	11.8 kB
Tags	Source
SHA-256 checksum How to use checksums	`fb8a74dcfc87ac8b397f8792913a4ed7c749d7fa22f8371de9d6d1d4ea71eb97`
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Uploaded via	`twine/6.2.0 CPython/3.14.2`

Release files / pytest_mqtt-0.7.0-py3-none-any.whl

Download URL	pytest_mqtt-0.7.0-py3-none-any.whl
Size	10.2 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`d3c003da758e6e5f8261c500d5bee8e11e3b419b5d789ce917ea9264fbb6638d`
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Upload date	Jan 28, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/6.2.0 CPython/3.14.2`