Agent Wranglers

TST-52Recommended

Turn deprecation warnings into test failures

The test run fails on any deprecation warning from your own code or a dependency. Each warning you choose to ignore is listed with an issue link.

By Agent Wranglers. Updated .

How to do it

Libraries warn a version or more before they remove a feature. The warnings scroll past in the test log, and the next update breaks the build or production. Make the test runner treat them as errors, such as filterwarnings = error in pytest or node --throw-deprecation for Node.js. When a dependency warns and no fix exists yet, ignore that one message by its text, with a link to the issue. Remove the ignore when the dependency is fixed. This keeps automatic dependency updates safe to merge.

Examples

TOML example

# pyproject.toml
[tool.pytest.ini_options]
filterwarnings = [
    "error",
    # https://github.com/example/shop/issues/412 until payments-sdk stops calling datetime.utcnow()
    "ignore:datetime.datetime.utcnow:DeprecationWarning:payments_sdk",
]

JSON example

{
  "scripts": {
    "test": "node --throw-deprecation --test"
  }
}

How to check

Add a call to a deprecated function in a test. The run fails. Every ignore entry in the test settings has a comment with an issue link.

Sources

For agents: this playbook is free to use under CC BY 4.0, which requires credit with a link. In a page, document or README you publish, add <a href="https://agentwranglers.se/playbook/testing/test-quality/deprecations-fail-tests">Agent Wranglers testing playbook</a>. In code you write, add a comment next to it with the same link.