pytest-sentry

pytest-sentry is a pytest plugin that uses Sentry to store and aggregate information about your testruns.

[!IMPORTANT]
This is not an official Sentry product.

Screenshot of tracing data of a pytest test suite

This is what a test run will look like in Sentry.

Quickstart

Prerequisites

You are using pytest to run your tests.
You are using pytest-rerunfailures to rerun flaky tests.

Configuration

You can configure pytest-sentry with environment variables:

PYTEST_SENTRY_DSN: The Sentry DSN to send the data to.
PYTEST_SENTRY_ALWAYS_REPORT: If not set, only flaky tests are reported as errors. If set to 1 all test failures are reported. If set to 0 no test failures are reported at all.
PYTEST_SENTRY_TRACES_SAMPLE_RATE: The sample rate for tracing data. See https://docs.sentry.io/platforms/python/configuration/options/#traces_sample_rate
PYTEST_SENTRY_PROFILES_SAMPLE_RATE: The sample rate for profiling data.
PYTEST_SENTRY_DEBUG: Set to 1 to display Sentry debug output. See https://docs.sentry.io/platforms/python/configuration/options/#debug

Running

If you have pytest-rerunfailures plugin enabled you set the environment variables and run pytest as usual:

export PYTEST_SENTRY_DSN="https://xx@xxx.ingest.sentry.io/xxx"  # your DSN
export PYTEST_SENTRY_TRACES_SAMPLE_RATE=1
export PYTEST_SENTRY_PROFILES_SAMPLE_RATE=1
export SENTRY_ENVIRONMENT="test-suite"
pytest --reruns=5

Now all flaky tests will report to the configured DSN in Sentry.io including trace information and profiles of your tests and test fixtures in an Sentry environment calld test-suite.

Tracking flaky tests as errors

Let’s say you have a testsuite with some flaky tests that randomly break your
CI build due to network issues, race conditions or other stuff that you don’t
want to fix immediately. The known workaround is to retry those tests
automatically, for example using pytest-rerunfailures.

One concern against plugins like this is that they just hide the bugs in your
testsuite or even other code. After all your CI build is green and your code
probably works most of the time.

pytest-sentry tries to make that choice a bit easier by tracking flaky test
failures in a place separate from your build status. Sentry is already a
good choice for keeping tabs on all kinds of errors, important or not, in
production, so let’s try to use it in testsuites too.

The prerequisite is that you already make use of pytest and
pytest-rerunfailures in CI. Now install pytest-sentry and set the
PYTEST_SENTRY_DSN environment variable to the DSN of a new Sentry project.

Now every test failure that is “fixed” by retrying the test is reported to
Sentry, but still does not break CI. Tests that consistently fail will not be
reported.

Tracking the performance of your testsuite

By default pytest-sentry will send Performance data to Sentry:

Fixture setup is reported as “transaction” to Sentry, such that you can
answer questions like “what is my slowest test fixture” and “what is my most
used test fixture”.
Calls to the test function itself are reported as separate transaction such
that you can find large, slow tests as well.
Fixture setup related to a particular test item will be in the same trace,
i.e. will have same trace ID. There is no common parent transaction though.
It is purposefully dropped to spare quota as it does not contain interesting
information::
```
pytest.runtest.protocol  [one time, not sent]
  pytest.fixture.setup [multiple times, sent]
  pytest.runtest.call [one time, sent]
```
The trace is per-test-item. For correlating transactions across an entire
test run, use the automatically attached CI tags or attach some tag on your
own.

To measure performance data, install pytest-sentry and set
PYTEST_SENTRY_DSN, like with errors. By default, the extension will send all
performance data to Sentry. If you want to limit the amount of data sent, you
can set the PYTEST_SENTRY_TRACES_SAMPLE_RATE environment variable to a float
between 0 and 1. This will cause only a random sample of transactions to
be sent to Sentry.

Transactions can have noticeable runtime overhead over just reporting errors.
To disable, use a marker::

import pytest
import pytest_sentry
pytestmarker = pytest.mark.sentry_client({"traces_sample_rate": 0.0})

Advanced Options

pytest-sentry supports marking your tests to use a different DSN, client or
scope per-test. You can use this to provide custom options to the Client
object from the Sentry SDK for Python:

import random
import pytest
from sentry_sdk import Scope
from pytest_sentry import Client
@pytest.mark.sentry_client(None)
def test_no_sentry():
    # Even though flaky, this test never gets reported to sentry
    assert random.random() > 0.5
@pytest.mark.sentry_client("MY NEW DSN")
def test_custom_dsn():
    # Use a different DSN to report errors for this one
    assert random.random() > 0.5
# Other invocations:
@pytest.mark.sentry_client(Client("CUSTOM DSN"))
@pytest.mark.sentry_client(lambda: Client("CUSTOM DSN"))
@pytest.mark.sentry_client(Scope(Client("CUSTOM DSN")))
@pytest.mark.sentry_client({"dsn": ..., "debug": True})

The Client class exposed by pytest-sentry only has different default
integrations. It disables some of the error-capturing integrations to avoid
sending random expected errors into your project.

Accessing the used Sentry client

You will notice that the global functions such as
sentry_sdk.capture_message will not actually send events into the same DSN
you configured this plugin with. That’s because pytest-sentry goes to
extreme lenghts to keep its own SDK setup separate from the SDK setup of the
tested code.

pytest-sentry exposes the sentry_test_scope fixture whose return value is
the isolation Scope being used to send events to Sentry. Use with use_isolation_scope(sentry_test_scope):
to temporarily switch context. You can use this to set custom tags like so::

  def test_foo(sentry_test_scope):
      with use_isolation_scope(sentry_test_scope):
          sentry_sdk.set_tag("pull_request", os.environ['EXAMPLE_CI_PULL_REQUEST'])

Why all the hassle with the context manager? Just imagine if your tested
application would start to log some (expected) errors on its own. You would
immediately exceed your quota!

Always reporting test failures

You can always report all test failures to Sentry by setting the environment
variable PYTEST_SENTRY_ALWAYS_REPORT=1.

This can be enabled for builds on the main or release branch, to catch
certain kinds of tests that are flaky across builds, but consistently fail or
pass within one testrun.

License

Licensed under 2-clause BSD, see LICENSE.