Requirements Based Testing Process Overview

Relative Cost to Fix an Error:
The reason for integrating testing earlier into the life cycle is simple economics. Studies have shown two things. First, that the majority of defects have their root cause in poorly defined requirements (see Figure 1). And second that the cost of fixing an error is cheaper the earlier it is found. The issue is scrap and rework. If a defect was introduced while coding, you just fix the code and re-compile. However, if a defect has its roots in poor requirements and is not discovered until integration testing then you must re-do the requirements, re-do the design, re-do the code, re-do the tests, re-do the user documentation, and re-do the training materials. It is all this “re-do” work that sends projects over budget and over schedule. Let’s say that a defect introduced during the
requirements phase is found during the requirements phase. Define the cost of finding that defect as 1X. If that same defect is not found until integration testing or production it will cost hundreds or even thousands of times more (see Figure 2).