The commit I69d95d153d6d1da1e019ae5ad2c3e7a4667971b5 for some reason now causes all quizzes on a page to be graded at once. You can verify this yourself by checking out the previous commit, verifying that only one Quiz is graded when you hit the submit button on a wiki page containing multiple quizzes, and checking out the later commit and verifying that all the quizzes are graded once any one submit button is hit. You should fix this bug.
Install mediawiki locally. It is easiest (often) to use vagrant for this. Quiz is not available as a role in vagrant, so follow these directions to manually add lines to LocalSettings.php in vagrant, and include the line
You can test that the extension is working by adding a sample quiz to your test wiki in wikitext.Y ou can export and then import the Help page from wikiversity for more comprehensive testing: here.
You can find the quiz extension in the vagrant repository by navigating to mediawiki/extensions/Quiz. If you haven't already, you will need to set up git, gerrit, and git-review, and install a gerrit hook to begin submitting commits to the Quiz extension.