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pytest-structlog

Structured logging assertions. pytest_ + structlog_ = pytest-structlog.

|pytest| |structlog|

Installation:

.. code-block:: bash

$ pip install pytest-structlog

Usage:

The fixture name is log. It has two attributes of interest: log.events is a list of events from captured log calls, and log.has is a helper function for asserting a single event was logged within the expected context.

Suppose you have some library module, your_lib, which is using structlog:

.. code-block:: python

your_lib.py

from structlog import get_logger

logger = get_logger()

def spline_reticulator(): logger.info("reticulating splines") for i in range(3): logger.debug("processing", spline=i) logger.info("reticulated splines", n_splines=3)

Then your test suite might use assertions such as shown below:

.. code-block:: python

test_your_lib.py

from your_lib import spline_reticulator

def test_spline_reticulator(log): assert len(log.events) == 0 spline_reticulator() assert len(log.events) == 5

   # can assert on the event only
   assert log.has("reticulating splines")

   # can assert with subcontext
   assert log.has("reticulated splines")
   assert log.has("reticulated splines", n_splines=3)
   assert log.has("reticulated splines", n_splines=3, level="info")

   # but not incorrect context
   assert not log.has("reticulated splines", n_splines=42)
   assert not log.has("reticulated splines", key="bogus")

   # can assert with the event dicts directly
   assert log.events == [
       {"event": "reticulating splines", "level": "info"},
       {"event": "processing", "level": "debug", "spline": 0},
       {"event": "processing", "level": "debug", "spline": 1},
       {"event": "processing", "level": "debug", "spline": 2},
       {"event": "reticulated splines", "level": "info", "n_splines": 3},
   ]

   # can use membership to check for a single event's data
   assert {"event": "reticulating splines", "level": "info"} in log.events

   # can use >= to specify only the events you're interested in
   assert log.events >= [
       {"event": "processing", "level": "debug", "spline": 0},
       {"event": "processing", "level": "debug", "spline": 2},
   ]

   # or put the comparison the other way around if you prefer
   assert [
       {"event": "processing", "level": "debug", "spline": 0},
       {"event": "processing", "level": "debug", "spline": 2},
   ] <= log.events

   # note: comparisons are order sensitive!
   assert not [
       {"event": "processing", "level": "debug", "spline": 2},
       {"event": "processing", "level": "debug", "spline": 0},
   ] <= log.events

.. _pytest: https://docs.pytest.org/ .. _structlog: https://www.structlog.org/ .. |pytest| image:: https://user-images.githubusercontent.com/6615374/46903931-515eef00-cea2-11e8-8945-980ddbf0a053.png .. |structlog| image:: https://user-images.githubusercontent.com/6615374/46903937-5b80ed80-cea2-11e8-9b85-d3f071180fe1.png