Unit testing with codeigniter 2.2

Take a look at this:  https://github.com/kenjis/ci-phpunit-test

It's currently for 3.x, but with some tweaking it should work with 2.x as well.

Unfortunately, I think tweaking it with 2.x is not so easy.
Because it is very tightly coupled with CI3. It replaces CI files including core files internally.
It was written for CI3 from scratch.

CI2 and 3 are similar to users, but 3 has a lot of lot of improvements (a little changes).
So if you use ci-phpunit-test with CI2, you need to take care of all the changes.

I recommend you upgrade CI to version 3, if you could. But if not, the following project
might help you:

https://github.com/fmalk/codeigniter-phpunit/tree/2.x

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper