An introduction to unit testing

1. Intro to Unit Testing

2. Module Overview
1. Why Tests Are Important
2. The Different Types of Tests
3. What is a Unit Test
4. Your First Unit Test - Hello World
5. What to Unit Test
6. Benefits of Unit Tests
7. What is *not* a Unit Test

3. Why are people writing unit tests?
 They need to prove they are smart
 They want to charge more
 They want to spend more time
coding before they ship
 They like more lines of code on
their stats
 They want to look good in
code reviews
 ?

4.  ?
Credit Card Validation (F5)

7. Credit Card Validation (with Unit Tests)

8. Save Time: Avoid Debuggerment
Whenever you are tempted to type something into a print statement or a debugger
expression, write it as a test instead. - Fowler

9. Pay a little now
or
Pay a lot later
Why are people writing unit tests?

10. Why Write Tests?

11. Why Tests Are Important
 Tests Reduce Bugs in New Features
 Tests Reduce Bugs in Existing Features
 Tests Are Great Documentation
 Tests Improve Design
 Testing Makes Development Faster
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#WhyUnitTests

12. The Different Types of Tests

13.  Smoke Tests
 Unit Tests
 Integration Tests
 Functional / Acceptance Tests
 Load Tests
 Stress Tests
Do You Know the Different Types of
Tests
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTes
ts.aspx#TypesOfTests

14. What is a Unit Test

15. Our First Unit Test
[TestMethod]
public void TestCalculation()
{
var orderManager = new OrderManager();
using (var db = new NorthwindDataContext())
{
var order = db.Orders.FirstOrDefault();
var actual = orderManager.GetTotalIncGST(order);
var expected = order.OrderItems.Sum(oi => oi.Qty * price) * 1.1;
Assert.AreEqual(actual, expected);
}
}

16. “A unit test is a fast, in-memory, consistent, automated and
repeatable test of a functional unit-of-work in the system.”
“A unit of work is any functional scenario in the system that contains
logic. It can be as short as a function, or it can span multiple
classes and functions, and it provides internal or business value to
the system under test.”
“Art of Unit Testing” Roy Osherove
What is a Unit test?

17. What makes something a UNIT test ?
Small: Validates a single concern / unit of work
Repeatable: You can rerun the same test as many times
as you want.
Consistent: Every time you run it, you get the same
result.
In Memory: It has no “hard” dependencies on anything
not in memory (such as file system, databases, network)
Fast: It should take a fraction of a second to run a unit test.

18. Readable
 Understand!
 What? Scenario? Expectation?
Maintainable
 We change our application
Trustworthy
 All  The code covered by unit tests works as expected
Attributes of a good Unit test

19. What is wrong with this test?
[TestMethod]
public void TestCalculation()
{
var orderManager = new OrderManager();
using (var db = new NorthwindDataContext())
{
var order = db.Orders.FirstOrDefault();
var actual = orderManager.GetTotalIncGST(order);
var expected = order.OrderItems.Sum(oi => oi.Qty * price) * 1.1;
Assert.AreEqual(actual, expected);
}
}

20. Hello Unit Tests – Your First Test

21. [TestClass]
public class StringValidationTests
{
[TestMethod]
public void IsValidEmailAddress_ForValidEmail_ReturnsTrue()
{
string email = "adam@stephensen.com";
bool result = email.IsValidEmailAddress();
Assert.IsTrue(result);
}
Let’s write a test

22. public static class StringValidation
{
public static bool IsValidEmailAddress(this string txtEmail)
{
return false;
}
Red

23. public static class StringValidation
{
public static bool IsValidEmailAddress(this string email)
{
Regex r = new Regex(@"^[w-]+(?:.[w-]+)*@(?:[w-]+.)+[a-zA-Z]{2,7}$");
Match match = r.Match(email);
return match.Success;
}
Green

24. [TestClass]
public class StringValidationTests_MSTest
{
[TestMethod]
public void IsValidEmailAddress_ForValidEmail_ReturnsTrue()
{
string email = "adam@stephensen.com";
bool result = email.IsValidEmailAddress();
Assert.IsTrue(result);
}
[TestMethod]
public void IsValidEmailAddress_ForEmailWithoutAmpersand_ReturnsFalse()
{
string email = "adamstephensen.com";
var result = email.IsValidEmailAddress();
Assert.IsFalse(result);
}
}
Test Both Ways

25. NUnit Test Fixtures
[TestFixture]
public class StringValidationTests_Nunit
{
[TestCase("adam@domain.com",Description="Valid simple email")]
[TestCase("adam-stephensen@domain-name.com", Description = "Valid email can contain hyphens")]
[TestCase("adam.stephensen.more@domain.com.au", Description = "Valid email with >1 periods")]
public void IsValidEmailAddress_ForValidEmails_ReturnsTrue(string email)
{
bool result = email.IsValidEmailAddress();
Assert.IsTrue(result);
}
[TestCase("adam@domain&more.com", Description = "Invalid email containing ampersand")]
[TestCase("@domain&other.com", Description = "Invalid email with no text before @")]
[TestCase("adam@", Description = "Invalid email with no text after @")]
[TestCase("adam@domain", Description = "Invalid email with no period after @")]
[TestCase("adam-domain.com", Description = "Email does not contain @")]
[TestCase("adam.@domain.com", Description = "Email cannot contain period directly before @")]
[TestCase("adam@.domain.com", Description = "Email cannot contain period directly after @")]
[TestCase(".adam@domain.com", Description = "Email cannot start with period")]
[TestCase("adam@domain.com.", Description = "Email cannot end with period")]
public void IsValidEmailAddress_ForInvalidEmail_ReturnsFalse(string email)
{
var result = email.IsValidEmailAddress();
Assert.IsFalse(result);
}
}

26. What to Unit Test

27. Do You Know What Code To Unit
Test?
Unit tests should be written for:
Fragile Code - e.g. Regular Expressions -
see below
When errors can be difficult to spot - e.g.
Rounding, arithmetic, calculations - see
below
Unit tests should not be written for:
Generated Code
Private methods
Dependencies - e.g. Database Schema,
Datasets, Web Services - see below
Performance - e.g. Slow forms, Time
critical applications - see below
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#HowMany

28. Test Fragile Code
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#RegEx

29. Tests for Complex Code
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#Arithmetic

30. Tests are the Best Documentation
Static
Documentation is
Technical Debt !
Unit Tests add
value!

31. Test Your JavaScript
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#TestJavascript

32. Benefits of Unit Tests

33.  Isolate each part of the program and check that the individual
parts work
 Strict, written contract that the piece of code must satisfy
 Allows you to refactor code and make sure it still works
correctly (regression testing)
Benefits of Unit Tests (1)

34.  Simplifies integration
 Testing the parts of a program first, and then testing their
integration
 Provides documentation
 Clients and other developers can look at their unit tests to gain
a basic understanding of the APIs and determine how to use
the module to fit their needs
 Improve code quality
 Code that cannot be easily tested is not factored properly
Benefits of Unit Tests (2)

35.  Code with automated validation reduces the time spent
manually testing, manually debugging, and hunting for errors
 Writing tests as the code is written lets you fail fast (find errors
early). Bugs are cheaper/faster to fix the earlier they are found
 Unit testing lets you refactor safely, finding any regressions as
they are introduced
Unit Tests Save Time

36. What is NOT a Unit Test

37. Pop Quiz – What’s NQR ?
[TestMethod]
public void TestCalculation()
{
var orderManager = new OrderManager();
using (var db = new NorthwindDataContext())
{
var order = db.Orders.FirstOrDefault();
var actual = orderManager.GetTotalIncGST(order);
var expected = order.OrderItems.Sum(oi => oi.Qty
* price) * 1.1;
Assert.AreEqual(actual, expected);
}
}
1. What are we testing?
2. Database Access !

38. It talks to the database
It communicates across the network
It touches the file system
It cannot be run in isolation from any other unit test
It can't run at the same time as any of your other unit tests
You have to do special things to your environment to run it
(e.g. editing config files / registry settings)
You are not testing a class in isolation from other concrete classes
When is a test *not* a Unit test?
http://www.ssw.com.au/ssw/standards/rules/RulesToBetterUnitTests.aspx#DependenciesDB

39. What is it ?
If it’s not a unit test…..

40.  Test the Integration of multiple components
 UI, Business Layer, Database
 Not in memory
 Touches
 File system
 Registry
 Database
 Other shared resources
Integration test

41. Run much slower
 not run in-memory
Less consistent
 Dependent from external resources
Has side effects
Harder to prepare
 E.g. Database setup
Integration test

42. Great when writing code to integrate to 3rd party APIs
Great for finding out when there is a problem with a large
complex system (is it the code, the database or a dependency)
Great for ensuring availability of external components
(zsValidate)
Integration test

43. Different Levels of Attention
Unit tests – should ALWAYS pass.
- Should be run on every CI Build
Integration tests – will sometimes be red
- Should be excluded from CI Build

44. Module Summary
1. Why Tests Are Important
2. The Different Types of Tests
3. What is a Unit Test
4. Your First Unit Test
5. What to Unit Test
6. Benefits of Unit Tests
7. What is NOT a Unit Test

45. Unit Testing References
 Roy Osherove
 Book http://www.artofunittesting.com/
 Blog http://weblogs.asp.net/ROsherove/
 Unit test definition
http://weblogs.asp.net/ROsherove/archive/2009/09/28/unit-test-definition-2-0.aspx
 Michael Feathers
 Blog http://www.artima.com/weblogs/index.jsp?blogger=mfeathers
 What is not a unit test? http://www.artima.com/weblogs/viewpost.jsp?thread=126923
 Unit Testing Rules
http://www.artima.com/weblogs/viewpost.jsp?thread=126923
 http://www.slideshare.net/nickokiss/unit-testing-best-practices
http://www.nickokiss.com/2009/09/unit-testing.html