Transcript Slide 1
Beyond Basic Unit Testing:
Mocks, Stubs, User Interfaces, & Refactoring for Testability Benjamin Day
Who am I?
• • • • • • Owner, Benjamin Day Consulting, Inc.
– Email: [email protected]
– – Web: http://www.benday.com
Blog: http://blog.benday.com
Trainer, Consultant – Visual Studio Team System, Team Foundation Server Microsoft MVP for VSTS Microsoft VSTS/TFS Customer Advisory Council Microsoft Cloud Services Advisory Group Leader of Beantown.NET INETA User Group
Shameless Plug
• • • This presentation is based on content from my training courses.
– Unit Testing & Test-Driven Development with Visual Studio (2 days) – Visual Studio Team System & Team Foundation Server (5 days) Public course schedule at http://benday.com
On-site training and consulting, too.
Copyright © 2007, Benjamin Day Consulting, Inc. www.benday.com
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Overview
• • • • Why do you care about unit testing?
Testing Problems Testing Solutions Code
WHAT & WHY?
What is Test Driven Development?
• • • Way of developing code so that you always have proof that something is working – Code that validates other code – Small chunks of “is it working?” Small chunks = Unit Tests Kent Beck (“Test-Driven Development”, Addison-Wesley) says “Never write a single line of code unless you have a failing automated test.”
What is a Unit Test?
• • Wikipedia says, “a unit test is a procedure used to validate that a particular module of source code is working properly” Method that exercises another piece of code and checks results and object state using assertions
Why Use TDD?
• • • • High-quality code – Fewer bugs – Bugs are easier to diagnose “Test First” method ~up-front design Less time spent in the debugger Tests that say when something works – Easier maintenance easier refactoring – Self documenting
Maximize Your QA Staff
• • • • You shouldn’t need QA to tell you your code doesn’t work Unit testing to minimizes the pointless bugs – “nothing happened” – “I got an error message” + stack trace – NullReferenceException QA should be checking for: – Meets requirements – Usability problems – Visual things (colors, fonts, etc) When you get a bug assigned to you it should add business value
PROBLEMS & SOLUTIONS
Testing Problems
• • • • Extra code just for the sake of the test Code coverage on exception handling Tendency toward end-to-end integration tests – Databases – WCF & Services – Big back-end systems Unit testing UIs
Testing Solutions
• • • • • • Mocks, Stubs, and Mocking Frameworks Interface-driven coding Factory Pattern and/or IoC Frameworks Repository Pattern Model-View-Presenter (MVP) Pattern Model-View-Controller (MVC) Pattern
Mocks vs Stubs vs Dummies vs Fakes • • • • • Martin Fowler http://martinfowler.com/articles/ mocksArentStubs.html
Dummy = passed but not used Fake = “shortcut” implementation Stub = Only pretends to work, returns pre defined answer Mock = Used to test expectations, requires verification at the end of test
RhinoMocks
• • • Dynamic Mocking Framework By Ayende Rahien http://ayende.com/projects/rhino-mocks.aspx
Free under the BSD license
RhinoMocks Primer
• • • • • MockRepository – Owns the mocking session StrictMock
Demo 1: Stub With RhinoMocks
Demo 2: Test Exception Handling
• • • Look at some existing code Refactor for testability Use RhinoMocks to trigger the exception handler
Avoid End-to-End Integration Tests
• • • Does a good test… …really have to write all the way to the database?
…really have to have a running WCF service on the other end of that call?
…really need to make a call to the mainframe?
The Repository Pattern
• •
“Mediates between the domain and data mapping layers using a collection-like interface for accessing domain objects.”
– http://martinfowler.com/eaaCatalog/repository.ht
ml Encapsulates the logic of getting things saved and retrieved
Person Repository
Demo 3: Repository Pattern
• Simplify database (or web service) unit test with a repository
USER INTERFACE TESTING
• • • • User Interfaces: The Redheaded Stepchild of the Unit Testing World Not easy to automate the UI testing Basically, automating button clicks UI’s almost have to be tested by a human – Computers don’t understand the “visual stuff” – – Colors, fonts, etc are hard to unit test for “This doesn’t look right” errors The rest is: – Exercising the application – Checking that fields have the right data – Checking field visibility
VSTS Web Tests
• • • • Record paths through your application Fills in form values Click buttons Validates • Difficult to do test-driven development
My $0.02
• • Solve the problem by not solving the problem Find a way to minimize what you can’t automate
The Solution.
• • • • • • • Keep as much logic as possible out of the UI – Shouldn’t be more than a handful of assignments – – Nothing smart Real work is handled by the business tier Test the business tier “Transaction Script” Pattern “Domain Model” Pattern “Service Layer” Pattern “Model View Presenter” Pattern “Model View Controller” Pattern
Service Layer Pattern
“Defines an application’s boundary with a layer of services that establishes a set of available operations and coordinates the application’s response in each operation.” -Randy Stafford
From “Patterns Of Enterprise Application Architecture” by Martin Fowler, Randy Stafford, et al.
Chapter 9
Model View Presenter (MVP)
Model View Presenter (MVP)
• •
The Common Tiers
Presentation tier • Business tier – ASP.NET
– Business object interfaces – Windows Forms – Business objects – – – WPF WCF Service The “View” of MVP – • The “Model” in MVP Business facades • Manipulate business objects • Handle requests for CRUD operations Presenter Tier – Handles the "conversation" between the presentation tier implementation and the business tier – – Defines the “View” Interfaces “Presenter” in MVP • • Data Access Tier Data Storage Tier – SQL Server
Tiering Up: Keep Logic Out Of The UIs • • • • Business Object Tier (Domain Model pattern) Business Façade Tier (Service Layer pattern) – Create new Business Object methods (Factory methods) – Wrap CRUD operations, abstract away data access logic – Duplicate name checks Create an interface to represent each page in your application Create Editor Facades as an adapter between the UI interfaces and the business objects Copyright © 2007, Benjamin Day Consulting, Inc. www.benday.com
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• • • • •
View interfaces
Interface represents the fields manipulated through the UI ASPX Page or Windows Form Implements the interface – Interface’s properties wrap UI widgets – ICustomerDetail.CustomerName
m_textboxCustomerName.Text
Use a stub represent the UI Write unit tests to test the functionality of the presenter Avoid business objects favor scalars
The Presenter
• • • Service Layer Pattern Wrap larger operations that are relevant to each UI page/screen interface – InitializeBlank(ICustomerDetail) – View(ICustomerDetail) – Save(ICustomerDetail) Since each page implements the interface, pass the page reference to the facade
Model View Presenter (MVP)
Designing the UI for Testability
PersonDetailView.aspx
Why is this more testable?
• • • • Each page/screen only has to get/set the value from interface property into the right display control UI does not know anything about business objects Doesn’t know about any details of loading or saving Doesn’t have to know about validation • All this logic goes into the editor façade and testable via unit test
Avoid Referencing Business Objects in the UI “interfaces” • ASP.NET
– Easier to write stateless pages (everything is in ViewState) – No need to try to re-create complex objects in code behind in order to save
Demo 4
• Refactor to UI Interfaces
Summary: Testing Solutions
• • • • • Mocks, Stubs, and Mocking Frameworks Interface-driven coding Factory Pattern and/or IoC Frameworks Repository Pattern Model-View-Presenter (MVP) Pattern
Who am I?
• • • • • • Owner, Benjamin Day Consulting, Inc.
– Email: [email protected]
– – Web: http://www.benday.com
Blog: http://blog.benday.com
Trainer, Consultant – Visual Studio Team System, Team Foundation Server Microsoft MVP for VSTS Microsoft VSTS/TFS Customer Advisory Council Microsoft Cloud Services Advisory Group Leader of Beantown.NET INETA User Group