How many people do unit testing?. Am always caught my deadline. I just fix errors in production. The client timeline are not feasible

Spending the extra time writing tests now will mean that you can debug issues faster in future. So in the long run it will actually speed you up. Imagine if you have a full suite of tests and you run them and everything passes. You make a small code change and some tests break. You can much more easily debug what went wrong because everything worked a minute ago before you made that change. Unit tests give you the confidence to go and make drastic changes to your code without the fear of breaking stuff.

Once you get into the habit of writing tests first, the code pretty much writes itself.