Testing Extensible Design Patterns in OO Frameworks through Scenario Templates D.S. Sanders Software Verification & Validation

Design Patterns Proven architectures for constructing flexible and maintainable software Promotes design reuse Language independent Neither classes nor objects

Origins & Progenitors The “Gang of Four”  Eric Gamma  Richard Helm  Ralph Johnson  John Vlissides Collectively penned “Design Patterns”: Elements of Reusable OO Software Written between ; released ‘95

Creational Patterns Abstract Factory* Factory Method* Builder Prototype Singleton

Structural Patterns Adapter Bridge Composite Decorator Façade Flyweight Visitor

Behavioral Patterns Chain of Responsibility Command Interpreter Iterator Mediator Momento Observer State Strategy* Template Method Visitor*

Post Gang of Four Patterns Architectural Patterns  Model – View – Controller Concurrency Patterns  Single Threaded Execution  Guarded Suspension  Balking  Read / Write Lock  Two Phase Termination

Memory Lane – Comp 110 Dynamic Typing  Some or all type checking done at runtime

More memory lane – Comp 110 Dynamic Binding  Determining at runtime the appropriate method to call

Pattern Categorization - Redux Static  Does not allow for easy extension  Behavior does not change after compile time  Easier to test Extensible  Allows functionality of the app to change  Adds new classes to the system  Some of the classes loaded at runtime

Factory Method Pattern

Factory Method Example

Strategy Pattern

Strategy Pattern Example

So much testing…so little time Scenario Based Testing Method Sequence Specification (MtSS) Message Sequence Specification (MgSS) Message Framework Specification (MfSS)

The Bank

MtSS of Account Class and MgSS of Method Withdraw

Message Framework Sequence Specs

Test Cases MfSS Slicing Partition Testing  Object Types  Number of / Groups of Objects  Object Input Space

More Memory Lane – Comp 380 Stress Testing Boundary Testing Negative Testing Random Testing

Compensating for Extensibility Testing Dynamic Typing Testing Dynamic Binding Testing Extensibility

Testing Results

Conclusion Testing Extensible Design Patterns is difficult MfSS will generate scenario templates which lead to test cases Use in Industry seems limited Source Code Credit  Kathy Sierra, Bert Bates (Factory, Strategy)  Collegeboard.org (GridWorld Case Study)