Posted by: ahmedashfaque | October 10, 2009

Cost of software testing

If you ever wondered how much it costs to test a software application? If you look at it from another angle, we should better ask how much it costs not to test a software application? A lot!

Yes it costs a lot more when a software application is not tested as compared to the scenario when it is tested. You may ask, how?

To explain it let us say, we have a software application of size 100,000 lines of source code. In normal circumstances, this size of application will have potential number of defects at around 500 (if we consider as defect density of  5 defects per 1000 lines of code. (OK, this may be higher than the normal rate but suppose this is true for our example).

Now suppose a test team of 2 software testers are employed to test the application. Each tester is given a salary of $3000 per month. Suppose they found 400 defects in one month of testing. The application was subsequently released. So the cost of testing in terms of dollars spent on testing will be $6000 for testers. Off course, there will be some more expense in terms of time spent by developers for fixing defects. Suppose the developers are paid $4000 per month. For each defect fixing, a developer takes 1 hour. So for fixing 400 defects, time spent by developers will be 400 hours. If a developer works 40 hours per week then it will take 10 weeks (2 and a half month) to fix all defects. So expense on fixing those defects will come to $10,000. So total cost of finding and fixing defects is $16,000.

Now suppose the application was not tested and it was released with all the 500 defects. In production, the application is to be supported by the software vendor. When end users find defects in the application, they report it to the vendor to fix the defects. When all those defects were reported by end users, the software vendor had no choice but to arrange for fixing these defects.

Suppose the software vendor had sold the software application to 10,000 customers. Each customer will ask for refunds from the license costs they paid to the software vendor due to the faulty software. Suppose the software vendor was forced to pay a refund of $100 to each customer. So he ends up spending $1,000,000 for refunds.

Now we can see that if the software vendor would have spent $16,000 for fixing defects then it would have been lot cheaper.

In the other words, not testing software application is more costly than testing it!


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