git - Reduce the chances of getting errors in a huge system -

i have online system sell games lottery. system create contests, generate games (for sort of different lotteries), manage results, verify these results, register clients, manage credits , create reports.

it got big , complex. system running , working still upgrading.

since entangled, every little change may cause catastrophe. system grows entropy.

i try reduce chances of errors testing, every time miss something. bringing me trouble lately.

what can reduce chances of error in big system one?

obs:

• yes, use git.
• i use codeigniter (mine hmvc).
• is place ask or should ask in stackexchange?

in major system that's doing lot of complex tasks, unit tests , integration tests going best friend. should have 2 projects within solution built specially purpose - 1 unit tests, , 1 integration tests.

while may seem boring or tedious do, written unit or integration test can save deploying broken code - typically you'll have group of tests run prior deployment, , if 1 of should fail, deployment halted way before goes out production.

this brings topic of code coverage, meaning basically, how of code testable? have test represent every unit of work application performs? these questions need ask you're writing tests. keep in mind, unit tests not helpful if don't have code coverage.

as starter, php development, phpunit great choice.

while may new concept you, find how unbelievably useful unit , integration tests can be, in development phase. there entire development methodology dedicated concept, called tdd. read on of these concepts, come coverage plan (what , want test), , try writing couple yourself.