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Unit testing using Visual Studio 2010 — WHY and HOW

As a developer, we have been asked about Unit testing during interviews. Typical answer is “yeah! i know how to write a unit test case but did not get a chance to implement it.”  what cliche! 🙂 .

Why Unit testing is important :  Apart from SDLC and following the best practices (from my experience nobody cares for unit test cases unless it is a established product). I still found one of the reasons why we may HAVE to perform unit testing for every application in future. Cloud Hosting is making news all around the world and looking at it’s cost benefits companies are trying their best to adopt it asap. With remote hosting comes lot of rules imposed by the vendor who is hosting your application and Unit testing is one of them. for example SFDC (sales force dot com) applications need at least 70% unit testing coverage of before they agree to host it on cloud.  So it’s about time we need to take unit testing seriously.

Good news for visual studio developers is that It’s really easy to implement unit testing in VS2010.  No plugins required for a test project.

Class Library : to unit test. I have a C# class library project. which has only one class  ProductRepository.cs. I am using entity framework to access database (makes life easy. right? :)).

</pre>
public class ProductRepository
 {
 public ProductRepository()
 {
 }
 private readonly static NorthwindEntities _db = new NorthwindEntities();

public static List<Product> GetAll()
 {
 return _db.Products.ToList();
 }

public static Product GetById(int productId)
 {
 return _db.Products.Where(p => p.ProductID == productId).SingleOrDefault();
 }
 }
<pre>

it has only two methods GetAll() and GetById(). You can change the implementation the way you need.

HOW to create a Unit Test using VS 2010: 

  1. Go to any class in library project. say ProductRepository class here.
  2. Go to any method name and Right Click and Select Create Unit Tests.

3.  It opens a wizard. It shows library with all types and its methods listed.  You can select types and methods you want to write unit test cases for.

4.  Select Output project. It can be an existing Test project or Select –> “Create a new C# Test project”

5.  It creates all the test methods for selected methods in library earlier in the wizard.

6.  Check out the Test method created for TestGetAll(). it prefixes “Test”  to all the method names.


[TestMethod()]
 public void GetAllTest()
 {
 List<Product> expected = null;

// change it here and make a db call to populate expected object with the same data source.

//something like below using entity framework.

// expected = _dbContext.Products.ToList();

 List<Product> actual;
 // call library method
 actual = ProductRepository.GetAll();
 Assert.AreEqual(expected, actual);
 Assert.Inconclusive("Verify the correctness of this test method.");
 }

7.  Note that Test project does not copy the .config  settings. Though it will reference the main project so database access layer classes are still available in test methods. Connection strings need to be added manually in test project .config.

8.   Look at a better implementation of TestGetAll () method below.


[TestMethod()]
 public void GetAllTest()
 {
 var _db = new NorthwindEntities(); // declared in class library
 List<Product> expected = null;
 expected = _db.Products.ToList();

 var actual = ProductRepository.GetAll();
 Assert.AreEqual(expected.Count , actual.Count );

// comparing each item in collection

IEnumerator<Product> p1 = expected.GetEnumerator();
 IEnumerator<Product> p2 = actual.GetEnumerator();

while (p1.MoveNext() && p2.MoveNext())
 {
 Assert.AreEqual(p1.Current.ProductID, p2.Current.ProductID);
 Assert.AreEqual(p1.Current.ProductName, p2.Current.ProductName);
 Assert.AreEqual(p1.Current.SupplierID, p2.Current.SupplierID);
 Assert.AreEqual(p1.Current.UnitPrice, p2.Current.UnitPrice);
 }
 }

Above code can be changed as per our needs. If you just want to validate the count of collection or each element.

How to Run Unit Test Cases: 

You will notice that under Solution Items there is a new file created YourClassLibraryProjectName.vsmdi . It will list out all the test methods. you can select the ones you want to run or Run all. Every time you make any changes in Test methods don’t forget to Refresh the .vsmdi file in Test editor.

Just Hit Run Test in Current context and check the results (Passed or Failed) in Test Results window. you should see something like the below.

It may look like coding twice for every method 🙂 but you got to do what you got to do. right?

I will go deeper in my next article “Unit Testing beyond Assert statements”. 

I hope it is useful!

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