Introduction to Unit Testing

Basic introduction to unit testing.

Transcript

1. P2P Code Academy Introduction to Unit Testing 27th June 2012
2. 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
3. Context
4. We All Have Tested Before • Manual tests • Least efficient
6. Unit Testing in Software • Functional Tests – Unit Tests – Integration Tests – System Tests – System Integration Tests • Non Functional Tests – Security, Performance, Usability…
7. What are Unit Tests
8. Integration Test Unit Test Tests that Test Units Of Code in Isolation low level
9. 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
10. Trustworthy Readable Maintainable
11. A Simple Unit Test
12. A Simple Unit Test
13. Unit Tests. Summary • Test Units of Code in Isolation • Automated and Repeatable • Easy to Implement and Run • Run Quickly • Trustworthy, Readable and Maintainable
14. Why Should I Care
15. Unit tests prove that your code actually works rnsure correctness works
16. Unit tests provide ultra-fast feedback demonstrate concrete progress increase productivity keeps you in the zone
17. 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
18. Unit tests provide high granularity bug detection reduces the cost of bugs pinpoint a bug to the method-level
19. Unit tests provide a living documentation it is always up-to-date it compiles! makes knowledge sharing easier
20. Unit Tests impose good design principles
21. Written by one, everyone benefits
22. Unit tests are one of the basic foundation components that enables continuous integration and continuous delivery
24. 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
25. How Does Unit Testing Work
26. All You Need Is Love • Unit Test Framework • Mocking Framework
27. The Unit Test Framework • Unit testing API • Test Runner
28. 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
29. The Unit Testing API • Way to mark code as test-code • Organize tests • Assertion library
30. Mark Code As Tests and Organizing Tests • Use of C# Attributes • [TestClass] and [TestMethod] • [TestCategory(“awesome-tests”)] • [Ignore]
31. 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
32. Basic Assertions • Static class Assert Assert.AreEqual<T>(T expected, T actual) Assert.AreNotEqual<T>(T noExpected, T actual) Assert.AreSame<T>(T expected, T actual) Assert.IsTrue(bool condition) Assert.IsFalse(bool condition) Assert.IsNull(object value) Assert.IsInstanceOfType(object value, Type expectedType)
33. 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)
34. Asserting Exceptions • [ExpectedException(typeof(MyException))]
35. The Unit Test Runner • Runs Tests • Provides feedback • Red/Yellow/Green
36. DEMO Using VS Testing Framework
37. 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
38. Mocks And Stubs Testing in Isolation
39. What happens when a class has dependencies?
40. Imagine...
41. Use Fake Objects to Isolate Class Under Text ensure that class under test is in complete isolation
42. What are Fake Objects crash test dummy simile
43. Two Types of Fake Objects • Stubs (passive testing) • Mocks (active testing)
44. 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
45. How To Create Fake Objects With Moq Bang! and you have a fake object that implements the IScreen interface! var fakeScreen = new Mock<IScreen>();
46. DEMO Using Moq
47. Using Moq. Summary 1. Install Moq using NuGet 2. Created two fake objects using Moq 3. Used fake objects to isolate the Calculator class
48. Testing Best Practices • Naming Conventions • AAA (Arrange Act Assert pattern) • Heuristics
49. Testing Naming Conventions
50. 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
51. 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
52. Disadvantages Of Unit Testing • None really, if well done – Write more Code – Maintain more code • If not well done, they have no value
53. Treat your tests as if they were production code
54. EXERCISE UNIT TESTING IN ACTION
55. Extra Goodies • Test Driven Development • Behavior Driven Development • Awesome Tools
56. Test Driven Development • Write test before production code • Test drives design • Test-Implement-Refactor cycle – Red/Green/Refactor
57. 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)
58. Behavior Driven Development
59. Awesome Tooling • NCrunch and Mighty Moose • Tests run always This test passed visual code coverage Code hasn’t been run yet status
60. And Remember...
61. If you want to know more...
62. If you want to know more...
63. 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
64. Thank you