10x reduction in post release defects – Finest experience of applying STEM

This is about one of the finest experiences that STAG had with a global chip major where the early implementation of STEM yielded significant results. Our engagement with them was to setup an effective validation practice for their porting level API for video decoders. The customer had a great technical team and were involved in both development and QA. The challenge that they faced with their complex product that involved both hardware and software and later system integration on multiple real time OS on various platforms, was that of high defect escapes i.e. post-release field defects.

We spent about a month understanding their domain and the associated technologies. Post this, a detailed analysis yielded interesting data – test cases were primarily conformance oriented, coverage of test cases was suspect, escaped defects seem to propagate from early stages and finally the process of validation was loose.

Having understood the types of defects that were being found and the post-release defects, we figured out the various types of probable defects and the various combinatorial aspects that need to be considered to form a test case. We then staged the validation as consisting of three major levels, the first one at API level, then the next one at a system level, and the last level made up of a customer-centric level that involved using reference applications.

Applying the STEM approach to test design, the test cases were developed, yielding about 6000 test cases at level one and about 800 at the subsequent levels. Also, whereas the ratio of +ve vs –ve test cases was earlier towards the +ve side, after our re-design, the ratio shifted to 60%:40% at the lower level and about 85% :15% at the higher levels. Moreover, the test cases increased in number significantly by a factor of 1000%, allowing for a larger and deeper net to catch many more serious defects. Over the next 9 months, the rate and number of defects detected increased dramatically, resulting in post-release issues reducing by a jaw-dropping 10x times.

Once we solved the test effectiveness problem and increased the yield of defects, the focus shifted to streamlining the process by setting up proper gating in the test process and creating a centralized web based test repository, and finally setting a strong defect analysis system based on Orthogonal Defect Classification (ODC) method. This enabled a strong feedback system, resulting in shifting the defect finding process to earlier stages of SDLC and thereby lowering cycle time. Complementing this, we focused on setting up a custom tooling framework for automating this non-UI based software resulting in a significant cycle time reduction – an entire cycle of tests on a platform took less than 15 hours of time!

This has been one of the finest experiences that we had with STEM, and was a clear winner for STEM implementation. This was only possible because of the very mature engineering management staff of the customer, who were focused on systemic improvement and had systematic improvement goals.

What is to be noted is that our test team was NOT a team with significant depth of experience on the particular product domain. Applying STEM at a personal level, the team was able to understand what was necessary and sufficient for effective validation and complemented the strong technical team with mature defect-oriented thinking. This was an early case study for us to establish that a STEM based approach provided us with the right thinking skills for defect finding, rather than resort to a domain centric approach to defect finding.

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