Diff-Cover

Diff cover is a tool that gives you a code coverage number on a diff rather than the entire project. The talk walks though how this works and discusses an tool that does the same but with quality tools like pep8

Transcript

1. Diff-Cover Bring your coverage from 0 to 100 one patch at a time Matt Bachmann
2. Batman Just Hired Us To Improve The Batputer
3. Lets check the project
4. Holy Untested Code Batman!
5. http://3.bp.blogspot.com/_x71ibPMLr4Y/TJu15YJoEaI/AAAAAAAAAys/Sy0lv3GCaEo/s400/LIL+SAD+BATMAN.jpg
6. Lets Talk Reality • We are on a deadline ◦ Covering the entire project may be infeasible • We don’t necessarily understand everything ◦ This can make for weak tests • But… we can at least improve going forward
7. Diff-Cover • Runs reports on Changes in a branch • Verify that any new change is covered by tests • Works with any language that can generate Cobertura XML reports (in theory)
8. So we write our new feature
9. Coverage has improved Very easy to stop here and say things are better.
10. Running Diff-Cover
11. Write More Tests! Bugs are a superstitious and cowardly lot. When tested they will show themselves. Developers must fight against chaos. Good tests are a critical tool.
12. Run it again!
13. WINNER! • You merge the code • The project is better than you found it • Batman is pleased to code that works for once http://dorkhorde.blogspot.com/2010/09/happy-little-batman.html
14. Diff Quality • Use static analyzers over Changes rather than the entire project • Today supports pep8, pyflakes, pylint
17. More features! • --fail-under option allows you to fail a build if the coverage percent or quality percent is not up to snuff ◦ Very nice when integrating into CI • --html-report Make super snazzy reports ◦ Display nicely with the html-publisher jenkins plugin
20. Acknowledgments • https://github.com/wedaly ◦ Creator of diff-cover • https://github.com/sarina ◦ Implemented diff-quality • 14 other contributors to date • https://github.com/bachmann1234/diff-cover
21. Slides: http://goo.gl/C3o6WG Me: @MattBachmann