Warning: As of Dec 2011 the tests haven't been kept to date and fail miserably
To test exercises, you need to also have the QUnit testing Framework in the directory khan-exercises/test/qunit. This is a separate download. Once you do that, you can navigate to these pages to see test results:
you should just be able to do a git submodule init; git submodule update from within the khan-exercises repo
user:~/khan-exercises/ $ git submodule init Submodule 'test/qunit' (https://github.com/jquery/qunit.git) registered for path 'test/qunit' user:~/khan-exercises/ $ git submodule update Cloning into test/qunit... remote: Counting objects: 1408, done. remote: Compressing objects: 100% (907/907), done. remote: Total 1408 (delta 636), reused 1253 (delta 495) Receiving objects: 100% (1408/1408), 228.73 KiB | 215 KiB/s, done. Resolving deltas: 100% (636/636), done. Submodule path 'test/qunit': checked out 'bd6a75e29e97576f12bed0c6d8f949d7bafcd9d7'
If that doesn't work, an alternative is this:
git clone http://github.com/jquery/qunit
cd khan-exercises/test ln -s ../../qunit qunit