Diff Coverage Tool
This tool combines the data collected by coverage.py with a diff to determine what if any lines modified or added in the diff are not covered in a coverage run (generally the running of the test suite).
Currently the implementation assumes this is for a Django patch for convenience, as that is what I needed at the time - but modifying should be pretty easy.
First run the Django test suite with coverage:
coverage run runtests.py --settings=test_sqlite
Assuming you are using git for development generate a diff that you want to use for comparison:
git diff master > /path/to/my_patch.diff
then from inside this tool's directory, you need to have your patched version of django on your python path, for example if you use a django-dev virtualenv:
python diff_coverage.py /path/to/my_patch.diff
The script will write to stdout files with patched, untested lines and generate an html report with those files and the lines highlighted (with a red line number) in the current working directory.