Introduction to Unit Testing

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P2P Code Academy Introduction to Unit Testing 27th June 2012

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Table Of Contents • Putting Things in Context • What is Unit Testing? • Why should I care? • How does it work? • Unit Tests in Action • Extra Goodies

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Context

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We All Have Tested Before • Manual tests • Least efficient

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Unit Testing in Software • Functional Tests – Unit Tests – Integration Tests – System Tests – System Integration Tests • Non Functional Tests – Security, Performance, Usability…

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What are Unit Tests

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Integration Test Unit Test Tests that Test Units Of Code in Isolation low level

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Automated and Repeatable • Run With One Click* • Deterministic • Once Written Remain For Future Use • Anyone Can Run Them • Easy to Implement and Run • Run Quickly * It can be fully automated

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Trustworthy Readable Maintainable

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A Simple Unit Test

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A Simple Unit Test

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Unit Tests. Summary • Test Units of Code in Isolation • Automated and Repeatable • Easy to Implement and Run • Run Quickly • Trustworthy, Readable and Maintainable

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Why Should I Care

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Unit tests prove that your code actually works rnsure correctness works

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Unit tests provide ultra-fast feedback demonstrate concrete progress increase productivity keeps you in the zone

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Unit tests provide a safety-net and a sense of security it’s more fun to code with them than without low-level regression test suite refactor mercilessly improve design without breaking it

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Unit tests provide high granularity bug detection reduces the cost of bugs pinpoint a bug to the method-level

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Unit tests provide a living documentation it is always up-to-date it compiles! makes knowledge sharing easier

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Unit Tests impose good design principles

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Written by one, everyone benefits

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Unit tests are one of the basic foundation components that enables continuous integration and continuous delivery

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Why Should I Care Wrap-Up • Prove That Your Code Works • Ultra-Fast Feedback • Safety Net & Sense of Security • Super High Granularity • Living Documentation (always up-to-date) • Impose Good Design Principles • Written by one, everyone benefits • Basic block for CI and CD

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How Does Unit Testing Work

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All You Need Is Love • Unit Test Framework • Mocking Framework

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The Unit Test Framework • Unit testing API • Test Runner

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Different Frameworks • Visual Studio Testing Framework (not MSTest) • NUnit • MbUnit • ... http://bit.ly/list-of-dotnet-unit-testing-frameworks use one and you pretty much can use all

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The Unit Testing API • Way to mark code as test-code • Organize tests • Assertion library

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Mark Code As Tests and Organizing Tests • Use of C# Attributes • [TestClass] and [TestMethod] • [TestCategory(“awesome-tests”)] • [Ignore]

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Assertion Library • Let’s you assert correctness • Provides a lot of built-in assertions • Microsoft.VisualStudio.TestTools.UnitTesting http://bit.ly/using-the-assert-classes

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Basic Assertions • Static class Assert Assert.AreEqual(T expected, T actual) Assert.AreNotEqual(T noExpected, T actual) Assert.AreSame(T expected, T actual) Assert.IsTrue(bool condition) Assert.IsFalse(bool condition) Assert.IsNull(object value) Assert.IsInstanceOfType(object value, Type expectedType)

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Assertions Also Available For • Collections AssertCollection • Strings AssertString CollectionAssert.AllItemsAreInstancesOfType(ICollection collection, Type type) CollectionAssert.AllItemsAreNotNull(ICollection collection) StringAssert.Contains(string value, string substring) StringAssert.StartsWith(string value, string substring)

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Asserting Exceptions • [ExpectedException(typeof(MyException))]

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The Unit Test Runner • Runs Tests • Provides feedback • Red/Yellow/Green

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DEMO Using VS Testing Framework

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Using Visual Studio Testing Framework. Summary 1. Created a Test project 2. Created a Test class 3. Created a method to test Calculator.Add() 1. Used AAA (Arrange, Act, Assert) pattern 4. Created a method to test Calculator.Substract() 5. Used [TestInitialize] and [TestCleanup] to make our test suite more maintanable 6. Illustrated what happens when a bug is introduced

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Mocks And Stubs Testing in Isolation

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What happens when a class has dependencies?

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Imagine...

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Use Fake Objects to Isolate Class Under Text ensure that class under test is in complete isolation

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What are Fake Objects crash test dummy simile

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Two Types of Fake Objects • Stubs (passive testing) • Mocks (active testing)

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Mocking Framework • Makes it easy to create Fake Objects • Lots of Mocking Frameworks: – Moq – RhinoMocks – EasyMock.NET – Nmock – … http://bit.ly/what-csharp-mocking-framework-to-use

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How To Create Fake Objects With Moq Bang! and you have a fake object that implements the IScreen interface! var fakeScreen = new Mock();

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DEMO Using Moq

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Using Moq. Summary 1. Install Moq using NuGet 2. Created two fake objects using Moq 3. Used fake objects to isolate the Calculator class

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Testing Best Practices • Naming Conventions • AAA (Arrange Act Assert pattern) • Heuristics

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Testing Naming Conventions

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General Heuristics • No logic in tests • Make sure the tests test only one thing • Separate unit tests from integration tests • Check test coverage by playing with values • Avoid code duplication

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General Heuristics II • Don’t abuse TestInitialize and TestCleanup • Make sure tests are isolated and repeatable • Most test should have one only assert • Only one mock per test • Use good naming conventions

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Disadvantages Of Unit Testing • None really, if well done – Write more Code – Maintain more code • If not well done, they have no value

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Treat your tests as if they were production code

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EXERCISE UNIT TESTING IN ACTION

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Extra Goodies • Test Driven Development • Behavior Driven Development • Awesome Tools

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Test Driven Development • Write test before production code • Test drives design • Test-Implement-Refactor cycle – Red/Green/Refactor

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Test Driven Development Benefits • You are the first user of your code • Only write the code you need to pass a test • Implement testable code • High test coverage • Increases productivity (red-green-refactor) • Increases quality (refactor)

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Behavior Driven Development

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Awesome Tooling • NCrunch and Mighty Moose • Tests run always This test passed visual code coverage Code hasn’t been run yet status

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And Remember...

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If you want to know more...

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If you want to know more...

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References • The Art Of Unit Testing http://amzn.to/the-art-of-unit-testing • Coding Horror http://bit.ly/i-pity-the-fool-who-doesnt-write-unit-tests

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Thank you