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Test Driven Development: By Example: is it worth reading?
The book that defined TDD, written as two worked examples rather than as a methodology.
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- published
- 2002
- key ideas
- 3
- reading path
- 1
Test Driven Development: By Example
by Kent Beck
- Publisher
- Addison-Wesley
- Year
- 2002
- ISBN
- 9780321146533
Useful when you are: Practising tester, Senior / lead
Verdict
Should you read it?
Read it if
You want to understand TDD from its source rather than from a summary. It is short and the worked examples carry the explanation better than any description.
Skip it if
You do not write production code, or you want guidance on testing an existing untested codebase. For that, read Feathers instead.
The argument
What it argues
Beck demonstrates TDD by doing it, at length, in two examples: a multi-currency money model and a small testing framework. You watch the red-green-refactor cycle applied step by step, including the steps that in hindsight were wrong.
The argument is that TDD is a design practice rather than a testing one. Writing the test first forces you to decide the interface before the implementation, and the discipline of taking small steps keeps you from building more than is needed.
The second example, building a testing framework using itself, is the more interesting half and the part people skip.
Key ideas
Ideas worth taking from it
- 01
Red, green, refactor
Write a failing test, make it pass in the simplest way, then improve the design with the test holding behaviour constant. The cycle that defines the practice.
- 02
TDD as design
The tests are a by-product. The value is being forced to specify the interface before the implementation, which produces more testable code almost incidentally.
- 03
Small steps and fake it till you make it
Deliberately writing an obviously insufficient implementation to get to green, then generalising. Counterintuitive and genuinely effective at avoiding over-building.
Criticism
What has dated, and what it gets wrong
The Java and Python examples are dated and the second example in particular feels archaic now. The deeper limitation is that it shows TDD on small, self-contained problems and says almost nothing about applying it to code with substantial dependencies, which is where most people actually get stuck.
Reading paths
On our reading paths
Becoming an automation engineer
Book 1 of 5 · Automation and SDET
Short and practical. It teaches the red, green, refactor rhythm and, more usefully, how small and focused a test can be.
- 1. Test Driven Development: By Example (this book)
2. Unit Testing Principles, Practices, and Patterns
3. Growing Object-Oriented Software, Guided by Tests
4. Working Effectively with Legacy Code
5. Specification by Example
Keep reading
What to read next
Reading about quality is cheaper than learning it in production.
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