What Is TDD?
What Is TDD?
A Way to Design Software Incrementally (while you code)
Two Ways To Design
Design before dev.Assumes requirements are stable
Implies design is the job of a designer
Can take a long time
Makes designer think ahead
Design during dev.Assumes requirements will change a lot
Design is the job of the programmers
Is real time
Focuses on current needs
Upfront vs. Incremental Design
Upfront designers:
Define abstractions
Incremental designers: Start from examples and extract
abstractions based on patterns
Test Driven Development
Write one test that describes a new behavior
Add the minimum of code to make it pass
Improve design by refactoring code and tests
Keep it Simple
Minimum code to make the current test pass
Keep it Clean
Refactor after each small change
Be in Flow
What's the next behavior?
What's the minimum change to implement it?
What's the right design?
Two Main Difficulties
Think at the problem, not the solutionProblem: I want to play
TicTacToe
Solution: We need four classes and a main method
Proof-based designProof-based: I see duplication, remove it by
creating a class
Assumption based: I will need a Game class
Start With TDD
How to Start?
What is the first test?
What is the next test?
Am I going in the right direction?
Remember
Incremental Design starts from examples, extracts abstractions
based on proof
Behavior Slicing
Identify Input and Output
Specify behaviors: input action output
Simplify: Identify first increment of the problem
Order behaviors so that only one thing changes
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