Tdd patterns1

AMIR BARYLKO
TDD PATTERNS
FOR .NET DEVELOPERS
SDEC 2010
DEVELOPER FOUNDATION TRACK

Amir Barylko - TDD Patterns MavenThought Inc.
Wednesday, October 13, 2010

WHO AM I?

• Architect

• Developer

• Mentor

• Great cook

• The one who’s entertaining you for the next hour!


WHY TDD?

• Test ﬁrst approach

• Quality driven

• Easy to refactor

• Regression tests as byproduct

• Increase developer’s conﬁdence


SETUP
Tools
AutoMocking
Movie Library


TOOLS

• Testing framework: NUnit, MbUnit, MSpec, rSpec

• Mocking framework: Rhino Mocks, Moq, TypeMock, nSubstitute

• Test Automation: Scripts that can run the test from the developer
computer.

• CI server: Unit test should be run after each commit, integration
tests, schedule tests.

• Reports and Notiﬁcations: The team should realize right away that
the tests are broken (broke the build jar).

MOVIE LIBRARY


AUTO MOCKING

• Automatic dependency creation for System Under Test

• Dictionary of dependencies to reuse by type

• Faster setup of tests without specifying creation

• Build your own: StructureMap

• Or use MavenThought Testing

• What about too many dependencies?

BEFORE AUTOMOCKING
protected IStorage Storage { get; set; } Deﬁne SUT
protected ICritic Critic { get; set } & Dependencies
protected MovieLibrary Sut { get; set; }

public void Setup()
{ Initialize each
this.Storage = Mock<IStorage>();

this.Critic = Mock<ICritic>();

this.Sut = new MovieLibrary(this.Storage, this.Critic)
}


AFTER AUTOMOCKING
SUT
public abstract class Specification
: AutoMockSpecificationWithNoContract<MovieLibrary>
{
}

public class When_movie_library_is_created : Specification
{
[It]
public void Should_do_something_with_critic()
{
Dep<IMovieCritic>().AssertWasCalled(...);
}
}
Dependency


PATTERNS
One feature at a time Dependency Injection
State Check Dependency Lookup
Behaviour Database
Parameters Smelly Test


ONE FEATURE PER TEST

• Easy to approach Given That
(arrange)
• Easy to understand
When I Run
• Easy to maintain
(act)
• Enforce Given, When, Then
Then it should ...
(assert)


XUNIT UNIT TESTING
[TestFixture]
public class MovieLibraryTest
{
private MockRepository _mockery;
private Library _library;
private IMovieCritic _critic;
[Test]
[SetUp]
public void WhenXXXX()
public void BeforeEachTest()
{
{
Assert.IsEmpty(_library.Contents);
this._mockery = new Mockery();
}
this._critic = _mockery.Create...;
this._library = new Library...
[Test]
}
public void WhenYYYYAndZZZAndWWWW()
{
[TearDown]
// record, playback, assert
public void AfterEachTest()
}
{
this._library.Clear();
}


ARRANGE ACT ASSERT
[Test]
public void When_Adding_Should_Appear_In_The_Contents()
{
// Arrange
var before = _sut.Contents.Count();

// Act
_sut.Add(_movie1);

// Assert
Assert.Contains(_sut.Contents, _movie1);
Assert.AreEqual(before + 1, _sut.Contents.Count());
}


ONE FEATURE
MANY SCENARIOS
Feature Speciﬁcation

When_xxxx.cs

When_yyyy.cs

When_zzzz.cs


FOCUS
[Specification]
public class When_movie_library_is_cleared : MovieLibrarySpecification
{
protected override void WhenIRun()
{
AddLotsOfMovies();

this.Sut.Clear();
}

[It]
public void Should_have_no_movies_in_the_library()
{
this.Sut.Contents.Should().Be.Empty();
}
}


CHECK THAT STATE!

• Care about the end state var m = new Library...

• Does not validate SUT
transitions Run Test

• Verify the state agains the
m.Count.Should(...)
expected value


WHY CHECK
IMPLEMENTATION?
[Specification]
public class When_movie_library_lists_non_violent_movies
: MovieLibrarySpecification
{
[It]
public void Should_call_the_critic()
{
Dep<IMovieCritic>().AssertWasCalled(c => c.IsViolent(...));
}
}


EXPECTED STATE
[Specification]
public class When_movie_library_lists_non_violent_movies
: MovieLibrarySpecification
{
[It]
public void Should_return_all_the_non_violent_movies()
{
this._actual.Should().Have.SameSequenceAs(this._expected);
}
}


BEHAVIOUR IS EVERYTHING

• Checking the expected var m = Mock<...>
behaviour happened

• Uses mock objects m.Stub(...)

• The behaviour is speciﬁed
for each mock object Run Test

• The expected methods
m.AssertWasCalled(...)
should be called


HOW ABOUT EVENTS?

• Where is the state?

• Should I create a concrete class?
[It]

public void Should_notify_an_element_was_added()
{
.......????
}


ASSERT BEHAVIOR
protected override void GivenThat()
{
base.GivenThat();

this._handler = MockIt(this._handler);

this.Sut.Added += this._handler;
}

[It]
public void Should_notify_an_element_was_added()
{
var matching = ...;
this._handler.AssertWasCalled(h => h(Arg.Is(this.Sut), matching));
}


PARAMETERS & FACTORIES
[Row(1)]
• Avoid duplication and [Row(2)]
repetition void Method(int arg)
[Row(typeof(...))]
• Generic Parameters void Method<T>(...)

• Parameters Factories [Factory(...)]
void Method(string arg)
• Random strings void Method([Random]...)

• Random numbers void Method([Random]...,
[Factory]...)


COMBINE
public When_movie_is_created(
[RandomStrings(Count=5, Pattern="The great [A-Za-z]{8}")] string title,
[Factory("RandomDates")] DateTime releaseDate)
{
this._title = title;
this._releaseDate = releaseDate;
}


DEPENDENCY INJECTION

• Remove hardcoded Initialize dependency
dependencies

• Introduces dependency in Stub dependency with
the constructor / setter mock

• Easy to test and maintain
Assert the mock is
returned
•S OLID


HARDCODED
DEPENDENCIES
public MovieLibrary()
{
this.Critic = new MovieCritic();
this._posterService = new SimplePosterService();
}

How are we going
to test it?


INJECT DEPENDENCIES
public MovieLibrary(IMovieCritic critic,

IPosterService posterService,

IMovieFactory factory)

: this(critic)

{

this._posterService = posterService;

this._factory = factory;

}


DEPENDENCY LOOKUP

• Remove hardcoded Initialize service
dependencies locator

• Introduces a factory or Stub to return a mock
service locator

• Easy to test and maintain Assert the mock is
returned
•S OLID


HARDCODED SERVICE
public void Import(IDictionary<string, DateTime> movies)

{

movies.ForEach(pair => this.Add(new Movie(...)));

}

Hardcoded!!!


FACTORY
public void Import(IDictionary<string, DateTime> movies)
{
movies.ForEach(pair => this.Add(this._factory.Create(...)));
}

COULD BE A
SERVICE LOCATOR....


DATABASE TESTING

• Base class to setup the Create Database
database

• The test always works with a Populate
clean database

• Can be conﬁgured to Store
populate data if needed

• To Retrieve and Assert
test only DB operations


USE TEMPORARY FILES
protected BaseStorageSpecification()
{
DbFile = Path.GetTempFileName();
}

protected override ISessionFactory CreateSut()
{
var factory = SessionFactoryGateway.CreateSessionFactory(SQLiteConfiguration
.Standard
.UsingFile(DbFile)
.ShowSql(), BuildSchema);

return factory;
}


CREATE & POPULATE
private void BuildSchema(Configuration config)
{
// delete the existing db on each run
if (File.Exists(DbFile))
{
File.Delete(DbFile);
}

// export schema
new SchemaExport(config).Create(true, true);
}


TEST DB OPERATIONS
[ConstructorSpecification]
public class When_movie_is_created : PersistentMovieSpecification
{
/// <summary>
/// Validates the mapping
/// </summary>
[It]
public void Should_have_the_right_mappings()
{
this.Sut.AutoSession(s =>
new PersistenceSpecification<Movie>(s)
.CheckProperty(p => p.Title, "Space Balls")
.VerifyTheMappings());
}
}


OMG: WHAT’S THAT SMELL?

• Setup is too big • Write only tests

• Hard to understand • Tests List<T>
dependencies
• Checking state between calls
• Needs SQL server running
with MsQueue and Biztalk • Inspect internals of the class

• Code coverage rules! • Can’t write a test for that

• No automation is possible

QUESTIONS?


THANK YOU!

• Contact me: amir@barylko.com, @abarylko

• Download: http://www.orhtocoders.com/presentations

• Books: The rSpec book, xUnit Patterns.


RESOURCES

• NUnit: http://www.nunit.org

• Gallio & MbUnit: http://www.gallio.org

• MavenThought Testing: http://maventcommons.codeplex.com

• Rhino Mocks: http://www.ayende.com

• StructureMap: http://structuremap.sourcefore.com

• TeamCity: http://www.jetbrains.com


Tdd patterns1

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