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Understanding Theory of Constraint has Helped Me in Effective Test Management

Posted on 1/08/2010 04:50:00 AM by Abhijeet Bhagat



Understanding Theory of Constraint has Helped Me in Effective Test Management
The popular theory of constraints proposed by Dr. Eliyahu M. Goldratt has always helped in doing effective test management. This post discusses the TOC in a nutshell and it application to management - be it Test management.

TOC originates from the idea that output of any system is limited by very small number of constraints. Constraints being anything that prevents the system from achieveing its goal.
Example 1: lets say that the at any given time 1000 vehicle can run on a highway per hour. From origin to destination if there were no constraints then the out of the system would be 1000.Now assume that there is a small tunnel on the highway and at any given time only 50 vehicle can pass through that tunnel per hour. Now What would be the out put of the system per hour? 1000? surely not and it would be merely 50 vehicle per hour reaching the destination.

The tunnel in above example is "Constraint" on the system. if we were to improve the efficiency of the system then the first thing that we would be doing is increase the throughput through this tunnel or simply bypass it.

Example 2: If there is an assembly line which has a capacity of producing 1000 engines but in some intermediate position we have recruited an unskilled labor who is churning out his parts far below the capacity what would happen? Wouldn't the following picture be true in this case?  In our day to day terminology we call this as "bottlenecks".

TOC : is essentially the management philosophy of identifying all such conatrtaints and eliminating those so that the system achieve its goal.

Toc is base on the assumption that anyssystem can be measured and controlled by following three measures :
  • Throughput : The money generated through sales.
  • Operating expenses :The money incurred on Operations.
  • Inventory :The money invested into ensuring services.
having understood this very basic intriduction to TOC let me illustrate how has it helped me in effective test management.

For me and my system(The Testing Team and processes) our goal is to achieve maximum coverage of the application and to test the application thoroughly enough with optimum resources and allocated budget.

  • What is My Throughput : The Number of test cases executed per day and the number of defects logged per day.
  • What are my operating  expenses: the day to day billing to the client and the cost incurred on my systems /softwares /electricity /the coomutation and a whole list of things incurred on employee.
  • What is my invetory : the costly KT sessions, the calls to understand the client requirement and the set of documentation produced for further references.
What are my constraints?
  1. The continuous availability of test environment, the test build deployed.
  2. The skilled manpower availability at all times.
  3. The continuous availability of my Test Case management / Defect management systems. and the list goes on.
Where were I actually creating bottlenecks into my system knowingly or unknowlingly?
  1. I am the only person who will review all the test cases / scripts. -  though skilled here is a bottleneck created.
  2. Testers are testing the application without much KT (Knowledge Transfer)being given to them? bottleneck, yes it is as i am not able to achive my goal -  The more number of defects.
  3. The people are testing effecively but the status reporting is taking good amout of time.bottleneck? yes it would be cause I making people slog.
How could the small subset of problem(among my gigantic) listed above were addressed later after analysing the constraints?
  1. Have 2-3 resources who could comfortably make a pass1 of the review so that atleast the bottleneck is prevented.
  2. KTs are essential and I should consider it as my operating expense. KT would ensure people understands the domian and the functinality.
  3. For effective test reporting - I then followed the best practice of tempaltizing documents /mails and all the artificats so that people now needed only to fill in the blanks.
I essentially followed on till i eliminated most of the constraints in the system. be it related to equipment, people or policy.
Not stopping at this point i ensured that i have sufficient buffers in every place so that if at all it is not possible to eliminate a constraint i would see that i feed sufficient work continuouly at the constraint point. How?

See. I had this constraint that a firmware module be tested by only the experts.in any case is not possible for a manual functional tester. This being my contstraint the possibility of creating abottleneck here would mean that the functional testers would just not be able to get their feed of work.I Applied the buffer(additional resources) in my case.One might think that buffers would add on to my operating expenses, true it does in fact it did but using the small percentage of incremnet my goal was achieved much more effectively.Once this extra resource was on the roll i was able to do better resource levelling for other manual functional resources.

The above and many more examples can be cited.TOC has helped me to look into the management with a new perspective.
In testing we normally say that its cheaper to catch the defect in a software in its early stages otherwise the cost increases logarithmically. Now is it not good to think test management from cost perspective? the preventive,appraisal and failure costs? we do we do think in that mannner extend this further and ask yourself where is my maximum cost being incurred - in prevention? in appraisal or in failures? and there you could find out that the cost being incurred more is becuase of some kind of constraint in the system.

Think of eliminating this casue. probably by reaching its root cause you'd be on your way to achieve you GOALS.




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