Check out example codes for "How to force run unit tests when running Git push?". It will help you in understanding the concepts better.

Code Example 1

while read oldrev newrev refname
    # Only run this script for the master branch. You can remove this 
    # if block if you wish to run it for others as well.
    if [[ $refname = "refs/heads/master" ]] ; then
        # Anything echo'd will show up in the console for the person 
        # who's doing a push
        echo "Preparing to run phpunit for $newrev ... "
        # Since the repo is bare, we need to put the actual files someplace, 
        # so we use the temp dir we chose earlier
        git archive $newrev | tar -x -C /home/jani/tmp/example
        echo "Running phpunit for $newrev ... "
        # This part is the actual code which is used to run our tests
        # In my case, the phpunit testsuite resides in the tests directory, so go there
        cd /home/jani/tmp/example/tests       
        # And execute the testsuite, while ignoring any output
        phpunit > /dev/null
        # $? is a shell variable which stores the return code from what we just ran
        if [[ $rc != 0 ]] ; then
            # A non-zero return code means an error occurred, so tell the user and exit
            echo "phpunit failed on rev $newrev - push deniend. Run tests locally and confirm they pass before pushing"
            exit $rc
# Everything went OK so we can exit with a zero
exit 0

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