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diff --git a/content/technical/git-coverage-useful-code-coverage.md b/content/technical/git-coverage-useful-code-coverage.md new file mode 100644 index 0000000..ca114a4 --- /dev/null +++ b/content/technical/git-coverage-useful-code-coverage.md @@ -0,0 +1,107 @@ +Title: git-coverage: Useful code coverage +Date: 2012-12-18 10:55 +Tags: technical, gnome +Slug: git-coverage-useful-code-coverage + +I've sorta dabbled in using code coverage off and on, but it never +really grabbed me as super useful and fit well within my workflow. + +When hacking on open source I want to try out patches, run tests against +them, whether automatic unit tests or manually diddling things during +testing. What I'm really interested is whether I tested out all the bits +of the patch. + +Traditional coverage tools tell you about the coverage of the whole +project, which you then have to update and dig through to see if your +changes were covered. I really don't care about the code coverage of +entire projects. This is especially true if I'm just a contributor of a +few patches. I want to see the coverage of the stuff I just changed. + + + +Anyhooo ... after much ongoing grumpiness ... I put together +[git-coverage][] which is a git plugin which you can use to look at a +patch and see which code paths have been run. Basically you use it +exactly like you would `git diff` but it highlights the code in the diff +that didn't have coverage. Works with Python, C and C++ code so far. + +<div class="separator" style="clear: both; text-align: center;"> + + + +</div> + +To use with C or C++ code, you need to build the project using gcc's +`--coverage` info. Something like this: + + :::text + $ CFLAGS='--coverage' ./configure ... + $ make clean all + + +Next you make some modifications to the code, rebuild, and run the tests +or code. Now the following command will tell you which of your changes +were covered. + + :::text + $ git coverage + + +Any lines that start with an exclam have no coverage. They're +highlighted in red if you have git coloring enabled. If there's no +output from the above command, then all lines have coverage. Similar to +how if nothing has changed, diff will output nothing. + +If you've already checked in your code then you would use the following +command to test the coverage of the last commit, similar to how you +might use git diff to show the last commit. + + + :::text + $ git coverage HEAD~1 + + +Or you can test coverage of the last N patches by doing stuff like: + + + :::text + $ git coverage HEAD~3.. + + +Normally `git-coverage` tries to check the coverage of lines surrounding +the changes. If you want to suppress this, you just pass in diff options +to narrow the diff down: + + + :::text + $ git coverage --unified=0 + + +To install `git-coverage` put it somewhere in your path. You might use: + + :::text + $ git clone git://thewalter.net/git-coverage + $ cd git-coverage + $ ln -s $PWD/git-coverage ~/.local/bin + +To use with Python code, install the `python-coverage` package, and run +your code or tests like this: + + + :::text + $ # Yup, python-coverage has a rather bold command name. + $ coverage run /path/to/python-code args ... + $ git coverage + +Anyway, maybe this'll help someone. It's an itch I've had for some +time. + +BTW, [Phillip][] put some [code into gnome-common][] which you can use +to [add --enable-code-coverage to your configure script][], and +optionally get full coverage reports for the project. Obviously also +works with git-coverage. + + [git-coverage]: http://thewalter.net/git/cgit.cgi/git-coverage/ + [Phillip]: http://tecnocode.co.uk/ + [code into gnome-common]: http://git.gnome.org/browse/gnome-common/tree/macros2/gnome-code-coverage.m4 + [add --enable-code-coverage to your configure script]: http://git.gnome.org/browse/gcr/commit/?id=a185f4f20f20776f6b0dcccb4f3eeba30941022a |