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First, Some History
Plan-Do-Check-Act
0 Originally called Plan-Do-Study-Act
0 Created by Walter Shewhart at Bell Labs during the
 1930s
Iterative & Incremental
           Development
0 The X-15 program in the 1950s used IID
Test-First in the Swinging 60s
0 X-15 team members seeded Project Mercury
   0 Time-boxed half-day iterations
   0 Tests w...
We were doing incremental development as early as 1957, in Los Angeles, under
the direction of Bernie Dimsdale [at IBM’s S...
Waterfall in the 1970s & 80s
0 Blame the DoD and the CMMI
Other stuff was happening
0 Object-orientation
   0 Simula from the late 60s
   0 Smalltalk in the 70s at Xerox PARC
0 Sof...
Into the 1990s
0 UML evolves
0 www arrives
What RUP was meant to be
What RUP actually was
RAD elaboration in the 90s
XP arrives
Test-Driven is in XP
Tests are Feedback in XP
Agile arrives
Agile is just XP, rebadged
and a Manifesto
The Philosophy of TDD
The Testing Game
0 Red:
   0 “Write a failing test”
0 Green:
   0 “Pass the failing test”
0 Refactor
   0 “Clean the imple...
Write a failing test
0 To know what test to write, you must:
   0 Analyze your problem
   0 Design your solution
   0 Code...
Agile Problem Analysis
0 System Metaphor
   0 Arises from the Architectural Spike
   0 A simple design with the defining q...
User Stories
0 A user story comprises one or more sentences in the
 everyday or business language of the end user that
 ca...
Agile Solutions
0 “Walk the solution”: for each user story
   0 Understand how this fits into the user experience
   0 Und...
Goldilocks Design
0 Design only what you need
  0 avoid YAGNI (You Ain’t Gonna Need It)
0 Reuse existing implementation
  ...
First Exercise
0 Brainstorm a realistic candidate application
0 Write a small set of user stories
0 Elaborate a user exper...
Analysis & Design
0 There are a variety of approaches to functional
  analysis and implementation design
0 The most common...
UML
0 The UML (Unified Modeling Language)
   0 It has the advantage that many developers have at least
     some familiari...
UML Use Case Diagram
0 Describes the functionality provided by a system in
 terms of actors and their goals represented as...
UML Activity Diagram
0 Used to describe the
 business and operational
 step-by-step workflows
 of components in a
 system
UML Sequence Diagram
0 Shows how processes operate with one another and
 in what sequence
UML Class Diagram
0 Describes the structure of a system by showing the
 system's classes, their attributes, methods, and t...
CRC Cards
0 Class Responsibility Collaboration cards are a
  brainstorming tool, proposed by Ward Cunningham and
  Kent Be...
CRC Card
Design Patterns
0 A general reusable solution to a commonly occurring
  problem within a given context
0 A design pattern ...
Some Creational Patterns
0 Factory method
   0 Define an interface for creating an object, but let derived classes decide
...
Some Structural Patterns
0 Adapter
   0 Convert the interface of a class into another interface clients
     expect
0 Brid...
Some Behavioural Patterns
0 Chain of responsibility
   0 Avoid coupling the sender of a request to its receiver by giving
...
Linguistics & Semantics
0 Using the meanings and
  relationships of words and
  phrases employed in the user
  stories and...
Personas
0 Fictional characters
 created to represent
 the different user
 types within a
 targeted
 demographic, attitude...
Storyboards
              0 A technique
                borrowed
                from the
                film
           ...
Second Exercise
0 Take one or more of the user stories from the first
  exercise and apply a selection of the analysis and...
Testing Frameworks
0 MSTest
   0 Built-in to Visual Studio
0 Pex
   0 Experimental white-box testing from MS Research
0 NU...
Arrange, Act, Assert
0 The default pattern for unit tests
   1. Arrange all necessary preconditions and inputs
   2. Act o...
Test naming conventions
0 Ad-hoc
   0 Anything goes
0 Behavioural
   0 Tests are named according to the behaviour under te...
xUnit Assertions
0 Fundamentals
   0   Assert.True(…) or Assert.False(…)
   0   Assert.Null(…) or Assert.NotNull(…)
   0  ...
System.Diagnostics.Debug
0 Assertions
   0 Debug.Assert(…)
   0 Debug.Fail(…)
0 Publication
   0 Debug.Print(…)
   0 Debug...
TDD at the Keyboard
1. Add a new test
2. Run all tests and see if the new one fails
3. Write some code
4. Run all tests an...
Exercise 3
0 Create a solution with two class libraries:
   0 TicTacToe
   0 TicTacToe.Facts
0 Add a reference to xUnit.ne...
Refactoring Code
0 A disciplined technique for restructuring an existing body of code,
  altering its internal structure w...
Refactoring Techniques
0 Techniques that allow for more abstraction
   0 Encapsulate Field: force code to access the field...
Exercise 4
0 Create a solution with two class libraries:
   0 RomanNumerals
   0 RomanNumerals.Facts
0 Use TDD to solve th...
Test Doubles
0 Objects that mimic real objects for testing purposes
   0 Dummies
     0 Have no behaviour or throw excepti...
Mocking Frameworks
0 Visual Studio doesn’t have one built-in
0 Moles
  0 Experimental framework from MS Research
0 Open so...
SOLID Code
0 Single Responsibility principle
   0 An object should have only a single responsibility
0 Open/Closed princip...
Inversion of Control
0 Microsoft
   0 Unity
   0 Common Service Locator
0 Open source
   0 Castle Windsor, Autofac, Struct...
Exercise 5
0 Create a solution with two class libraries:
   0 Translator
   0 Translator.Facts
0 Use TDD to solve the prob...
Test Driven Development (C#)
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Test Driven Development (C#)

  1. 1. First, Some History
  2. 2. Plan-Do-Check-Act 0 Originally called Plan-Do-Study-Act 0 Created by Walter Shewhart at Bell Labs during the 1930s
  3. 3. Iterative & Incremental Development 0 The X-15 program in the 1950s used IID
  4. 4. Test-First in the Swinging 60s 0 X-15 team members seeded Project Mercury 0 Time-boxed half-day iterations 0 Tests were written first 0 Reviews after each iteration 0 Top-down development with stubs
  5. 5. We were doing incremental development as early as 1957, in Los Angeles, under the direction of Bernie Dimsdale [at IBM’s Service Bureau Corporation]. He was a colleague of John von Neumann, so perhaps he learned it there, or assumed it as totally natural. I do remember Herb Jacobs (primarily, though we all participated) developing a large simulation for Motorola, where the technique used was, as far as I can tell, indistinguishable from XP. When much of the same team was reassembled in Washington, DC in 1958 to develop Project Mercury, we had our own machine and the new Share Operating System, whose symbolic modification and assembly allowed us to build the system incrementally, which we did, with great success. Project Mercury was the seed bed out of which grew the IBM Federal Systems Division. Thus, that division started with a history and tradition of incremental development. All of us, as far as I can remember, thought waterfalling of a huge project was rather stupid, or at least ignorant of the realities… I think what the waterfall description did for us was make us realize that we were doing something else, something unnamed except for “software development.” Gerald M. Weinberg
  6. 6. Waterfall in the 1970s & 80s 0 Blame the DoD and the CMMI
  7. 7. Other stuff was happening 0 Object-orientation 0 Simula from the late 60s 0 Smalltalk in the 70s at Xerox PARC 0 Software distribution
  8. 8. Into the 1990s 0 UML evolves 0 www arrives
  9. 9. What RUP was meant to be
  10. 10. What RUP actually was
  11. 11. RAD elaboration in the 90s
  12. 12. XP arrives
  13. 13. Test-Driven is in XP
  14. 14. Tests are Feedback in XP
  15. 15. Agile arrives
  16. 16. Agile is just XP, rebadged
  17. 17. and a Manifesto
  18. 18. The Philosophy of TDD
  19. 19. The Testing Game 0 Red: 0 “Write a failing test” 0 Green: 0 “Pass the failing test” 0 Refactor 0 “Clean the implementation”
  20. 20. Write a failing test 0 To know what test to write, you must: 0 Analyze your problem 0 Design your solution 0 Code intentionally 0 To dislike “Big Upfront Design” is not to dislike design
  21. 21. Agile Problem Analysis 0 System Metaphor 0 Arises from the Architectural Spike 0 A simple design with the defining quality of explaining the system design without reference to documents 0 User Experience 0 Arises from the set of all user stories 0 Provides a canvas onto which individual stories can be painted 0 User Story 0 Describes a specific user expectation 0 Provides the functional constraints of implementation
  22. 22. User Stories 0 A user story comprises one or more sentences in the everyday or business language of the end user that captures what the user wants to achieve
  23. 23. Agile Solutions 0 “Walk the solution”: for each user story 0 Understand how this fits into the user experience 0 Understand where the necessary functional implementation goes in the architecture 0 Design the functional implementation
  24. 24. Goldilocks Design 0 Design only what you need 0 avoid YAGNI (You Ain’t Gonna Need It) 0 Reuse existing implementation 0 be DRY (Don’t Repeat Yourself) 0 Prefer sketched designs over definitive design 0 allow TDD to be part of your design process 0 Don’t experiment in code 0 use spikes where necessary
  25. 25. First Exercise 0 Brainstorm a realistic candidate application 0 Write a small set of user stories 0 Elaborate a user experience 0 Articulate a system metaphor 0 Time limit: one hour
  26. 26. Analysis & Design 0 There are a variety of approaches to functional analysis and implementation design 0 The most commonly used are: 0 The UML 0 CRC Cards 0 Design Patterns 0 Linguistics & Semantics 0 Personas 0 Storyboards
  27. 27. UML 0 The UML (Unified Modeling Language) 0 It has the advantage that many developers have at least some familiarity 0 It has the disadvantage of significant complexity 0 Most agile practitioners use ‘sketch’ UML, typically on a whiteboard, in order to convey a mental model of a proposed solution 0 Be indicative, not definitive
  28. 28. UML Use Case Diagram 0 Describes the functionality provided by a system in terms of actors and their goals represented as use cases
  29. 29. UML Activity Diagram 0 Used to describe the business and operational step-by-step workflows of components in a system
  30. 30. UML Sequence Diagram 0 Shows how processes operate with one another and in what sequence
  31. 31. UML Class Diagram 0 Describes the structure of a system by showing the system's classes, their attributes, methods, and the relationships among the classes
  32. 32. CRC Cards 0 Class Responsibility Collaboration cards are a brainstorming tool, proposed by Ward Cunningham and Kent Beck 0 They are typically used when determining which classes are needed and how they will interact 0 CRC cards are usually created from index cards on which are written: 0 The class name 0 Any base or derived classes (if applicable) 0 The responsibilities of the class 0 The names of other classes with which the class will collaborate to fulfil its responsibilities
  33. 33. CRC Card
  34. 34. Design Patterns 0 A general reusable solution to a commonly occurring problem within a given context 0 A design pattern is not a finished design that can be transformed directly into code; it is a description or template for how to solve a problem that can be used in many different situations 0 Typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved
  35. 35. Some Creational Patterns 0 Factory method 0 Define an interface for creating an object, but let derived classes decide which class to instantiate 0 Lazy initialization 0 Tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed 0 Object pool 0 Avoid expensive acquisition and release of resources by recycling objects that are no longer in use 0 Resource acquisition is initialization 0 Ensure that resources are properly released by tying them to the lifespan of suitable objects 0 Singleton 0 Ensure a class has only one instance, and provide a global point of access to it
  36. 36. Some Structural Patterns 0 Adapter 0 Convert the interface of a class into another interface clients expect 0 Bridge 0 Decouple an abstraction from its implementation allowing the two to vary independently 0 Facade 0 Provide a unified interface to a set of interfaces in a subsystem 0 Proxy 0 Provide a surrogate or placeholder for another object to control access to it
  37. 37. Some Behavioural Patterns 0 Chain of responsibility 0 Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request 0 Command 0 Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations 0 Iterator 0 Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation 0 Null object 0 Avoid null references by providing a default object
  38. 38. Linguistics & Semantics 0 Using the meanings and relationships of words and phrases employed in the user stories and other material to construct a language map of the problem domain 0 Especially useful when dealing with ‘expert’ systems
  39. 39. Personas 0 Fictional characters created to represent the different user types within a targeted demographic, attitude and/or behaviour set that might use a site, brand or product in a similar way
  40. 40. Storyboards 0 A technique borrowed from the film industry 0 Shows the user experience in sequence
  41. 41. Second Exercise 0 Take one or more of the user stories from the first exercise and apply a selection of the analysis and design techniques 0 Draw up a list of the strengths and weaknesses of the techniques in relation to these particular user stories 0 Time limit: one hour
  42. 42. Testing Frameworks 0 MSTest 0 Built-in to Visual Studio 0 Pex 0 Experimental white-box testing from MS Research 0 NUnit 0 Early open source port of JUnit for .net 0 MbUnit 0 Another open source framework 0 xUnit 0 Open source reset of NUnit 0 SpecFlow 0 Open source behaviour-driven-development framework
  43. 43. Arrange, Act, Assert 0 The default pattern for unit tests 1. Arrange all necessary preconditions and inputs 2. Act on the object or method under test 3. Assert that the expected results have occurred
  44. 44. Test naming conventions 0 Ad-hoc 0 Anything goes 0 Behavioural 0 Tests are named according to the behaviour under test 0 Good fit for collaboration tests (distinct from unit tests) public void customer_pays_in_cheque_to_current_account() 0 Contractual 0 Names follow the unit contract under test http://alandean.blogspot.com/2011/11/unit-test-naming-convention.html
  45. 45. xUnit Assertions 0 Fundamentals 0 Assert.True(…) or Assert.False(…) 0 Assert.Null(…) or Assert.NotNull(…) 0 Assert.Equal(…) or Assert.NotEqual(…) 0 Assert.Same(…) or Assert.NotSame(…) 0 Exceptions 0 Assert.Throws<T>(…) or Assert.DoesNotThrow(…) 0 Type checks 0 Assert.IsType(…) or Assert.IsNotType<T>(…) 0 Assert.IsAssignableFrom<T>(…) 0 IEnumerable 0 Assert.Empty(…) or Assert.NotEmpty(…) 0 Assert.Single(…) 0 Assert.Contains(…) or Assert.DoesNotContain(…) 0 Assert.InRange(…) or Assert.NotInRange(…)
  46. 46. System.Diagnostics.Debug 0 Assertions 0 Debug.Assert(…) 0 Debug.Fail(…) 0 Publication 0 Debug.Print(…) 0 Debug.Write(…) or Debug.WriteIf(…) 0 Debug.WriteLine(…) or Debug.WriteLineIf(…)
  47. 47. TDD at the Keyboard 1. Add a new test 2. Run all tests and see if the new one fails 3. Write some code 4. Run all tests and see them succeed 5. Refactor code 6. Repeat
  48. 48. Exercise 3 0 Create a solution with two class libraries: 0 TicTacToe 0 TicTacToe.Facts 0 Add a reference to xUnit.net in the Facts library 0 http://nuget.org/ 0 Use TDD to implement Tic-Tac-Toe 0 http://gojko.net/2009/08/02/tdd-as-if-you-meant-it-revisited/ 0 Time limit: one hour
  49. 49. Refactoring Code 0 A disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behaviour 0 Usually motivated by noticing a code smell 0 There are two general categories of benefits to the activity of refactoring 0 Maintainability 0 It is easier to fix bugs because the source code is easy to read and the intent of its author is easy to grasp 0 This might be achieved by reducing large monolithic routines into a set of individually concise, well-named, single-purpose methods 0 It might be achieved by moving a method to a more appropriate class, or by removing misleading comments. 0 Extensibility 0 It is easier to extend the capabilities of the application if it uses recognizable design patterns, and it provides some flexibility where none before may have existed
  50. 50. Refactoring Techniques 0 Techniques that allow for more abstraction 0 Encapsulate Field: force code to access the field with getter and setter methods 0 Generalize Type: create more general types to allow for more code sharing 0 Replace Conditional with Polymorphism: move each leg of the conditional to an overriding method in a derived class and make the original method abstract 0 Techniques for breaking code apart into more logical pieces 0 Extract Method: turn part of a larger method into a new method 0 Extract Class: moves part of the code from an existing class into a new class 0 Techniques for improving names and location of code 0 Move Method or Field: move to a more appropriate class 0 Rename Method or Field: changing the name to one that better reveals its purpose 0 Pull Up: move to a base class 0 Push Down: move to a derived class 0 Longer list 0 http://martinfowler.com/refactoring/catalog/index.html
  51. 51. Exercise 4 0 Create a solution with two class libraries: 0 RomanNumerals 0 RomanNumerals.Facts 0 Use TDD to solve the problem 0 https://sites.google.com/site/tddproblems/all-problems-1/Roman-number-conversion 0 Refactor the code as you go 0 Time limit: one hour
  52. 52. Test Doubles 0 Objects that mimic real objects for testing purposes 0 Dummies 0 Have no behaviour or throw exceptions 0 Stubs 0 Provide the behaviour of a real object 0 Spies 0 Record activity for later verification 0 Mocks 0 Define the expected activity before the test is run 0 Fakes 0 Employ a simpler implementation such as an in-memory database 0 See also http://martinfowler.com/articles/mocksArentStubs.html
  53. 53. Mocking Frameworks 0 Visual Studio doesn’t have one built-in 0 Moles 0 Experimental framework from MS Research 0 Open source 0 Moq, NCrunch, NMock2, Rhino Mocks, fakeiteasy 0 Commercial 0 TypeMock Isolator, JustMock
  54. 54. SOLID Code 0 Single Responsibility principle 0 An object should have only a single responsibility 0 Open/Closed principle 0 Objects should be open for extension, but closed for modification 0 Liskov Substitution principle 0 Objects should be replaceable with instances of their derived types without altering correctness 0 Interface Segregation principle 0 Many client specific interfaces are better than one general purpose interface 0 Dependency Inversion principle 0 Depend upon abstractions; do not depend upon concretions
  55. 55. Inversion of Control 0 Microsoft 0 Unity 0 Common Service Locator 0 Open source 0 Castle Windsor, Autofac, StructureMap, Ninject, LinFu
  56. 56. Exercise 5 0 Create a solution with two class libraries: 0 Translator 0 Translator.Facts 0 Use TDD to solve the problem 0 TODO 0 Refactor the code as you go 0 Use test doubles to isolate tests from dependencies and resources to achieve SOLID code 0 Time limit: two hours
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