Refactoring Away from

Test Hell@alastairs

alastair@alastairsmith.me.uk http://www.codebork.com/

The Graduate

The Junior

The Software Engineer

Tests are your parachute

•Getting to Green

•Use Mocks Wisely

•Document the System

Getting to Green

Do what you need to get there

1. Invest in the infrastructure

2.Fake the infrastructure

3. Isolate yourself from the infrastructure

Invest in the infrastructure

• Add more build agents

• Run tests in parallel

• Beefier hardware

• Fix infrastructure issues

Fake the infrastructure

• Introduce a seam

• A place where you can alter behaviour without editing in that place

• Use Value Objects for your inputs and outputs

• Try Record-Replay

Record-Replay

Short-term hack!

• Fake the seam interface

• Save requests to disk

• Respond immediately if a known request

• Compare artefacts against a known-good version

Isolate yourself from the infrastructure

• Refactor your seams

• Introduce mocks

Use Mocks Wisely

Mocking Rules of Thumb

• Don’t mix mocks and stubs

• Don’t nest mocks

• Use strict mocks

• Only mock types you own

It’s a Unit of Behaviour, Dammit!

• Test your interface, not your implementation

• Use Collaboration and Contract tests (http://j.mp/10UFgOS)

[Test]public void Moq_Example_With_A_Mock(){ // Arrange var mock = new Mock<IProductRepository>(MockBehavior.Strict); mock.Setup(r => r.Save(pen)); // Test fails if not included var sut = new AddProductsCommand(mock.Object);

// Act sut.Add(pen);

// Assert mock.Verify(r => r.Save(pen)); // Behaviour Verification}

[Test]public void Moq_Example_With_A_Stub(){ // Arrange    var stub = new Mock<IProductRepository>(MockBehavior.Strict);    stub.Setup(r => r.GetProduct(1)).Returns(pen); // Pre-condition    var sut = new AddProductsCommand(stub.Object);

// Act    var actual = sut.Get(1);

// Assert    var expected = pen;    Assert.That(actual, Is.EqualTo(expected));}

Document the System

General tips

• Use Descriptive And Meaningful Phrases

• Use a defined structure with conventions

• Make anonymous data obviously anonymousvar anonymousText = "Anonymous Text";

• Use randomised data for large input spaces

• Keep to a Cyclomatic Complexity of 1

SUT Factory

• Decouples tests from construction logic

• Protects you from changes to the constructor signature

• Consider the Fixture Object pattern

SUT: System Under Test

Test Builders

• A Domain-Specific Language in your tests

• Clarify intent

• Use for anything with

• Non-trivial construction

• Varied setup

• Test Data

• The SUT

[Fact]public void Placing_An_Order_Adds_The_Order_To_The_Customers_Account(){ // Arrange var customer = new Customer( 1, // Id "Joe", "Bloggs", // Name "10 City Road", "Staines", "Middlesex", "AB1 2CD" // Address ); var order = new Order(1, customer);

// Act, Assert: not interesting for this example}

[Fact]public void Placing_An_Order_Adds_The_Order_To_The_Customers_Account(){ // Arrange var customer = ACustomer() .WithGivenName("Joe") .WithFamilyName("Bloggs") .Build(); var order = AnOrder().PlacedBy(customer).Build();

// Act, Assert: not interesting for this example}

Bob the Builder

• Maintains Fluent syntax

• Reduces boilerplate

• Install-Package BobTheBuilder

using BobTheBuilder;

[Fact]public void Placing_An_Order_Adds_The_Order_To_The_Customers_Account(){ // Arrange var customer = A.BuilderFor<Customer>() .WithGivenName("Joe") .WithFamilyName("Bloggs") .Build(); var order = new Order(1, customer);

// Act, Assert: not interesting for this example}

using BobTheBuilder;

[Fact]public void Placing_An_Order_Adds_The_Order_To_The_Customers_Account(){ // Arrange Customer customer = A.BuilderFor<Customer>() .With(givenName: "Joe", familyName: "Bloggs"); var order = new Order(1, customer);

// Act, Assert: not interesting for this example}

Assertions

• Keep to one logical assertion per test

• Aim for Equality assertions

• Write custom constraints / matchers

• Consider the Fixture Object pattern

Test-Specific Equality

• IEqualityComparer<T>

• Resemblance

• Likeness

AutoFixture

• Automates many of the techniques described here

• Install-Package AutoFixture

• Support for all popular mocking frameworks

[Test, AutoData]public void IntroductoryTest(int expectedNumber, MyClass sut){ int result = sut.Echo(expectedNumber);    Assert.Equal(expectedNumber, result);}

• Getting to Green

• Do what you need to get there

• Use Mocks Wisely

• Don’t nest mocks

• Use strict mocks

• Write Contract and Collaboration Tests

• Document the System

• SUT Factory

• Test Builders

• Assertions

References and Resourceshttp://j.mp/refactoringTestHell

xUnit Patterns (Gerard Meszaros): http://j.mp/11bV67X

Integration Tests are a Scam (J B Rainsberger): http://j.mp/10UFgOS

Boundaries (Gary Berhardt): http://j.mp/1o18XbT

Advanced Unit Testing (Mark Seemann, Pluralsight): http://j.mp/psAdvUT

Any questions?@alastairs

alastair@alastairsmith.me.uk http://www.codebork.com/