Skip to main content

An abundance of coverage data

Project description




Build Status

Smother is a wrapper utility around that measures code coverage separately for each test in a test suite. Its main features include:

  • Fast and reliable coverage tracking using

  • Ability to lookup which tests visit an arbitrary section of your application code.

  • Ability to convert version control diffs into a subset of affected tests to rerun.


Smother contains plugins for nose and pytest, and behaves similarly to

py.test --smother=my_module test_suite/
nosetests --with-smother --smother-package=my_module test_suite/

These commands create a .smother file that can be queried by the smother CLI

smother lookup          # which tests visited module
smother lookup  # or just some lines in that file?
smother lookup      # or just the `baz` function?

smother diff                    # given local modifications to my repo, what tests might have broken?
smother diff | xargs py.test    # just run them!

smother to_coverage             # build a vanilla .coverage file from a .smother file
smother csv test.csv            # dump all (application, test) pairs to a file


Smother was designed to make it easier to work with legacy codebases. Such codebases often have several properties that make rapid iteration difficult:

  • Long-running test suites. The initial codebase that smother was designed for took nearly 24 hours of CPU time to run its 11K tests. smother diff makes it easier to select a (hopefully much) smaller subset of tests to re-run to quickly identify possible regressions.

  • Many different subsystems – most of which any single developer is unfamiliar with. smother lookup can be used to explore how and where particular modules are invoked in a test suite. These tests often reveal implicit contracts about code behavior that are not obvious from documentation alone.

  • Scope creep. Over time the abstractions in codebases become leakier, and logic between different subsystems becomes more heavily coupled. smother csv catalogs the coupling between source code units (lines, functions, or classes) and tests. Exploring this data often yields insights about which subsystems are well-encapsulated, and which would benefit from refactoring.

Full Documentation

Read the Docs

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

smother-0.1.tar.gz (17.4 kB view hashes)

Uploaded Source

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page