Friday, February 28, 2014

Test Estimation in Scrum Environment

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One of the most important activities in Agile methodology is estimation of user stories. Estimation of user stories forms two parts viz. development estimation and test estimation of these user stories.

I would like to drill more into test estimation of user stories (though similar analogy can be applied to development estimation as well) and one of the methods that can used to arrive at some justifiable figure. The estimation is always provided in terms of story points where each story point corresponds to 1 day of work ,i.e. 6 hours ( = 8 - 2 unproductive hours :) ). Hence 1 story point measures 6 hours of work.

Consider a user story which requires 60 hours of test efforts. Once the feature is developed and it is quite possible that there are defects observed post initial round of testing. Assuming that defect that are generated and fixed consume 15 % of test efforts that were initially planned, it is now required to add these 15 % hours to the initial test efforts ,i.e 60 + 15 percent of (60) = 64 hours. Also post testing these defects it is also safe to assume some more defects could be observed that may further add 10 percent of  ( 15 percent of (60) ) hours  =  0.4 hours.

Hence total test estimate of user story jumps from initial 60 hours to 64.4 hours ( = 64 + 0.4 ). The story point for this user story would be 64.4 hours / 6 hours (refer to second para from the top) = 10.7 rounded to 11.

Hence test estimation for our user story is 11 points or 64.4 hours. This can further be converted into weeks or days based on the unit that one would like to follow.

We have to keep on refining these estimates over each sprint so that our estimates are aligned with actual estimates for upcoming or next sprint user stories.

Is there any other method that can be used to arrive at test estimates? Comments are welcome.

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