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While learning to develop in PHP it has been easy enough that my short, one page, 20 line little scripts I could add "testing code" directly to my functions to figure out where I am or get close to the area in the code where the issue is found (for example, "print_r($var)," "var_dump($var)," "print 'you are here') type stuff.
Now that my code bases are growing lines and lines deep and accross multiple files, it's becoming a pain to go through and uncomment out all of my test code, and then go back and recomment it out again once an issue is resolved.
Recently I have discovered git in managing my larger applications. I've latched onto branches, and I have a testing branch and production branch I jump between when debugging. The testing branch of course has all my 'print this or that' testing code.
However, this still doesn't feel right.
As code grows, what are ways I can test and debug it? What are best practices for testing and debugging code as applications get larger and more complex? The phrase "Unit testing" catches my eye now and then, but it's still unfamiliar to me. Is this something I should be paying attention more to? Do large projects have different testing and production code bases and is a version control system the correct way to approach managing it?