Refer followings :
1) It may not be practical/right to do unit testing as a seperately identifiable activity if your project duration is short. Typically I shall not suggest you to consider this activity for projects having size less than 30 MM (Man Months).
2) For big projects you should do it, especially when you adopt phased delievery model. Estimate 20-30% of coding time for Unit Testing but make sure that this activity nver exceeds than 10% of overall project time.
Ratio for QA/QC versus Testing you can estimate as 1:1 and w.r.t. total project time both should never exceed 30%.
I suggest start putting dates, time, numbers somewhere on your scribbling pad, task sheet or whatever tracking you do at your place and later collate the actuals w.r.t. what estimates you used as reference. In 2-3 quarters you will be expert in all this.
I think this is very project (and even task) dependant. In the extreme cases there might even be coding tasks which taskes less time to implement than to test. It depends on the amount of other code (components) interfacing with the tested unit, and the complecity of the required testing environment. Thus, when making such a plan, you should consider the component under development and not apply some rule automatically.
Sometimes our job is of maintenance- we make changes to the existing code units or add new code units to existing Modules. We only know the purpose of the change/addition we're making. We do not know the functionality of the whole module. We're even given the logic we've to apply.
How do I test such tasks and what should be the percentage of time required for testing in this case?
Kshama it seems that you are from delhi even i am working in delhi want to know about you and your email id as because we are from the same field. i am also Test eng. working for last 5 years. so please i will ask you some question.
Asking Questions in this forum itself will be more beneficial for you as many other more experienced people may help you. Secondly, other people can also benefit from the discussions.
I guess you will need to apply explorative reseaching if scope is as vague as you described. In such cases you can take the estimate of 1 MD (ManDay) per 5k LOC (Line Of Code). This is not standard figure but with time you would be able to smooth this figure in nex quarters. I suggest start using numbers as numbers are important notr only for number crunchers and R&D stream but also for visibility about testing status.