Test-Driven Development: Extensive Tutorial

Front Matter

Dedications

Thanks!

About code examples

1. Notes for C# users
2. Notes for Java users
3. Part 1: Just the basics
4. Status: stable

Motivation – the first step to learning TDD

1. What TDD feels like
2. Let’s get it started!

The essential tools

1. Test framework
2. Mocking framework
3. Anonymous values generator
4. Summary

It’s not (only) a test

1. When a test becomes something more
2. Taking it to the software development land
3. A Specification rather than a test suite
4. The differences between executable and “traditional” specifications

Statement-first programming

1. What’s the point of writing a specification after the fact?
2. “Test-First” means seeing a failure
3. “Test-After” often ends up as “Test-Never”
4. “Test-After” often leads to design rework
5. Summary

Practicing what we have already learned

1. Let me tell you a story
2. Act 1: The Car
3. Act 2: The Customer’s Site
4. Act 3: Test-Driven Development
5. Epilogue

Sorting out the bits

How to start?

1. Start with a good name
2. Start by filling the GIVEN-WHEN-THEN structure with the obvious
3. Start from the end
4. Start by invoking a method if you have one
5. Summary

How is TDD about analysis and what does “GIVEN-WHEN-THEN” mean?

1. Is there a commonality between analysis and TDD?
2. Gherkin
3. TODO list… again!

What is the scope of a unit-level Statement in TDD?

1. Scope and level
2. On what level do we specify our software?
3. What should be the functional scope of a single Statement?
4. Failing to adhere to the three rules
5. How many assertions do I need?
6. Summary

Developing a TDD style and Constrained Non-Determinism

1. A style?
2. Principle: Tests As Specification
3. First technique: Anonymous Input
4. Second technique: Derived Values
5. Third technique: Distinct Generated Values
6. Fourth technique: Constant Specification
7. Summary of the example
8. Constrained non-determinism
9. Summary

Specifying functional boundaries and conditions

1. Sometimes, an anonymous value is not enough
2. Exceptions to the rule
3. Rules valid within boundaries
4. Combination of boundaries – ranges
5. Summary

Driving the implementation from Specification

1. Type the obvious implementation
2. Fake it (‘til you make it)
3. Triangulate
4. Summary
5. Part 2: Object-Oriented World
6. Status: pretty stable
7. Teaching one thing at a time

On Object Composability

1. Another task for Johnny and Benjamin
2. A Quick Retrospective

Telling, not asking

1. Contractors
2. A Quick Retrospective

The need for mock objects

1. Composability… again!

Why do we need composability?

1. Pre-object-oriented approaches
2. Object-oriented programming to the rescue!
3. The power of composition
4. Summary – are you still with me?

Web, messages and protocols

1. So, again, what does it mean to compose objects?
2. Alarms, again!
3. Summary

Composing a web of objects

1. Three important questions
2. A preview of all three answers

When are objects composed?

How does a sender obtain a reference to a recipient (i.e. how connections are made)?

1. Receive as a constructor parameter
2. Receive inside a message (i.e. as a method parameter)
3. Receive in response to a message (i.e. as a method return value)
4. Receive as a registered observer

Where are objects composed?

1. Composition Root
2. Factories
3. Summary

Interfaces

1. Classes vs interfaces
2. Events/callbacks vs interfaces – few words on roles
3. Small interfaces

Protocols

1. Protocols exist
2. Protocol stability
3. Craft messages to reflect the sender’s intention
4. Model interactions after the problem domain
5. Message recipients should be told what to do, instead of being asked for information
6. Most of the getters should be removed, return values should be avoided
7. Protocols should be small and abstract
8. Summary

Classes

1. Single Responsibility Principle
2. Static recipients
3. Summary

Object Composition as a Language

1. More readable composition root
2. Refactoring for readability
3. Composition as a language
4. The significance of a higher-level language
5. Some advice
6. Summary

Value Objects

1. What is a value object?
2. Example: money and names

Value object anatomy

1. Class signature
2. Hidden data
3. Hidden constructor
4. String conversion methods
5. Equality members
6. The return of investment
7. Summary

Aspects of value objects design

1. Immutability
2. Handling of variability
3. Special values
4. Value types and Tell Don’t Ask
5. Summary
6. Part 3: TDD in Object-Oriented World
7. Status: under development

Mock Objects as a testing tool

1. A backing example
2. Interfaces
3. Protocols
4. Roles
5. Behaviors
6. Filling in the roles
7. Using a mock channel
8. Mocks as yet another context
9. Summary

Test-first using mock objects

1. How to start? – with mock objects
2. Responsibility and Responsibility
3. Channel and DataDispatch one more time
4. The first behavior
5. Second behavior – specifying an error
6. Summary

Test-driving at the input boundary

1. Fixing the ticket office
2. Initial objects
3. Bootstrap
4. Writing the first Statement
5. Summary

Test-driving at the input boundary – a retrospective

1. Outside-in development
2. Workflow specification
3. Data Transfer Objects and TDD
4. Using a ReservationInProgress
5. Interface discovery and the sources of abstractions
6. Do I need all of this to do TDD?
7. What’s next?

Test-driving object creation

Test-driving object creation – a retrospective

1. Limits of creation specification
2. Why specify object creation?
3. What do we specify in the creational Statements?
4. Value object creation
5. Summary

Test-driving application logic

1. Summary

Test-driving value objects

1. Initial value object
2. Value semantics
3. Case-insensitive comparison
4. Input validation
5. Summary

Reaching the web of objects boundaries

1. What time is it?
2. Timers
3. Threads
4. Others

What’s inside the object?

1. What are object’s peers?
2. What are object’s internals?
3. Examples of internals
4. Summary

Design smells visible in the Specification

1. Design smells’ catalog
2. General description
3. Flavors

THIS IS ALL I HAVE FOR NOW. WHAT FOLLOWS IS RAW, UNORDERED MATERIAL THAT’S NOT YET READY TO BE CONSUMED AS PART OF THIS TUTORIAL

Mock objects as a design tool

1. Responsibility-Driven Design

Guidance of test smells

1. Long Statements
2. Lots of stubbing
3. Specifying private members

Revisiting topics from chapter 1

1. Constrained non-determinism in OO world
2. Behavioral boundaries
3. Triangulation

Maintainable mock-based Statements

1. Setup and teardown

Refactoring mock code

1. Part 4: Application architecture

On stable/architectural boundaries

Ports and adapters

1. Physical separation of layers

What goes into application?

1. Application and other layers

What goes into ports?

1. Data transfer objects
2. Ports are not a layer
3. Part 5: TDD on application architecture level

Designing automation layer

1. Adapting screenplay pattern
2. Driver
3. Actors
4. Data builders

Further Reading

1. Motivation – the first step to learning TDD
2. The Essential Tools
3. Value Objects