Bearded-android-docs

Created Tuesday 22 April 2014

Chapter 7 - It Takes Forever to Make a Change

• minimize dependencies by extracting interfaces

Chapter 8 - How Do I Add a Feature?

TestDrivenDevelopment:

0. Get the class you want to change under test.
1. Write a failing test case.
2. Get it to compile.
3. Make it pass. (Leave legacy code unchanged as much as possible)
4. Remove duplication.
5. Repeat.

• use ProgrammingByDifference up until it makes sense. Ensure LiskovSubstitutionPrinciple by using a NormalizedHierarchy and you may have to ultimately use ObjectComposition

Chapter 9 - I Can't Get This Class Into a Test Harness

i.e., can't instantiate a class.

Difficult Constructors

• extracting an interface for a difficult class that's a parameter in a constructor
• try passing null to one of the parameters (works only in Java/C#)

Hidden Dependencies

• +ParameterizeConstructor --- make the hidden dependency explicit in a new constructor and don't break existing code by having the old constructor call the new

Construction Blob

• Occurs when parameterizing constructor would result in a very large parameter list OR constructor creates objects with parameters
• try +SupersedeInstanceVariable --- add a setter to override the object that gets created in the constructor

Global Dependencies

• In Java/C#, occurs when constructor uses a singleton object
• try +IntroduceStaticSetter --- add a setter in the singleton class to override/reset singleton instance