Critique of Test Design Axioms in The Tester’s Pocketbook Rikard Edgren

The Tester’s Pocketbook by Paul Gerrard is not a great book, but it is very good.
It covers fundamentals of software testing, and contains a ton of good ideas that will help you in your testing effort.
I also like it because it is one of few books on testing theory that focus on the human element of software, and its creation.

However, I disagree with some things, and will focus on the test design part.
These are Gerrard’s test design axioms with my verdict:

Test Model – Test Design is based on models
Yes, use many, and also look outside them. Build your own quality characteristics model.

Test Basis – Testers need sources of knowledge to select things to test
Yes, use multiple information sources to understand what is important, the list is bigger though (Purpose, Capabilities, Failure Modes, Quality Characteristics, Usage Scenarios, Creative Ideas, Models, Data, Surroundings, White-box, Public Collections, Internal Collections, Business Objectives, Information Objectives, Product Image, Product Fears, Project Risks, Rumors, Product History, Project Background, Test Artifacts, Debt, Business Knowledge, Field Information, Users, Conversations, Actual Software, Technologies, Standards, References, Competitors, Tools, Context Analysis, Legal Aspects, Many Deliverables, Searching, You.)

Oracle – Testers need sources of knowledge to evaluate actual outcomes or behaviors
Very useful, but not necessary; we can sometimes suspend judgment and communicate noteworthy information.

Coverage – Testing needs a test coverage model or models
Not needed, unless as a tool to get more test ideas, or a way to report what has been tested. Gerrard’s question “how many tests remain?” is not good. A better one is “how much test time do you guess remain?”

Prioritisation – Testing needs a mechanism for ordering tests by value
Don’t waste too much time on this; when necessary use a fast, frugal test triage.
Page 38 states “we must invite stakeholders to take an utilitarian view.” This is not true. We could equally well use a value-based system, e.g. “bought software should not crash”, or just go by feelings about what is right.

Fallibility – Our sources of knowledge are fallible and incomplete
True, but text gets a bit too negative towards the human mind. An engaged mind can make mistakes, but also discover what is important. We can separate right from wrong, we can handle the unknown, we can make up for mistakes done.

So which axiom is missing?
Sampling & Serendipity – testing is inevitably a sampling activity, where serendipity is to our help.

There is also an overall problem when Gerrard states that these axioms are needed to do testing. It should be: needed to do good testing.
Nonetheless, one of the better testing books out there!

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