Book Image

Software Test Design

By : Simon Amey
Book Image

Software Test Design

By: Simon Amey

Overview of this book

Software Test Design details best practices for testing software applications and writing comprehensive test plans. Written by an expert with over twenty years of experience in the high-tech industry, this guide will provide you with training and practical examples to improve your testing skills. Thorough testing requires a thorough understanding of the functionality under test, informed by exploratory testing and described by a detailed functional specification. This book is divided into three sections, the first of which will describe how best to complete those tasks to start testing from a solid foundation. Armed with the feature specification, functional testing verifies the visible behavior of features by identifying equivalence partitions, boundary values, and other key test conditions. This section explores techniques such as black- and white-box testing, trying error cases, finding security weaknesses, improving the user experience, and how to maintain your product in the long term. The final section describes how best to test the limits of your application. How does it behave under failure conditions and can it recover? What is the maximum load it can sustain? And how does it respond when overloaded? By the end of this book, you will know how to write detailed test plans to improve the quality of your software applications.
Table of Contents (21 chapters)
Part 1 – Preparing to Test
Part 2 – Functional Testing
Part 3 – Non-Functional Testing
Appendix – Example Feature Specification

Identifying positive feedback loops

Positive feedback loops can cause chaotic behavior and catastrophic reductions in performance, where adding load increases failures, which adds even more load:

Figure 13.4 – A positive feedback loop of loading failures producing even more load

Inefficient processing can be due to failures requiring more system resources, for instance, due to writing large error logs or remote calls to indicate a problem. Additional retries can be caused by faults in the client logic, such that some failures lead to even more requests and even more failures.

Recall the example of self-inflicted DDoS from Chapter 7, Testing of Error Cases. There, positive feedback resulted in more load and even more failures. We saw an example when we read conference details from Outlook for all our users: the system was overwhelmed, and writing the logs for all the failures only slowed it down further.

Often these failures are emergent behavior...