An introduction to unit testing
0 likes658 views
The document discusses introductory concepts and best practices for unit testing, including: 1. Why unit tests are important for reducing bugs, improving design, and making development faster. 2. The different types of tests like unit tests, integration tests, and functional tests. 3. What constitutes a unit test, including that it is small, repeatable, consistent, and fast. 4. An example of writing a "Hello World" unit test in C#.
![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);
}
}](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-15-320.jpg)
![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);
}
}](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-19-320.jpg)
![[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](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-21-320.jpg)
![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](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-23-320.jpg)
![[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](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-24-320.jpg)
![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);
}
}](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-25-320.jpg)
![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 !](https://image.slidesharecdn.com/1801-unit-testing-intro-170210034449-181017141931/85/An-introduction-to-unit-testing-37-320.jpg)
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
- 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!
- 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