Unit Testing Data-Driven WCF Services
// March 27th, 2009 // No Comments » // .net, Unit Tests, design patterns, services, wcf
Any data driven module, class or method needs to be tested. At this moment anything that is data-drive (which would actually cover almost anything) needs to be verified according to specs to ensure correctness. In this post we will talk about creating tests for Data-Driven WCF Services. For simplicity and ease of use, we are going to use the Enterprise Library Data Application Block to talk to the database.
Before we get deeper into the topic at hand, let’s talk about the unit test environment that I use and recommend for testing data-driven applications.
Testing Context
The basic objective of a unit test is to verify correctness of a an application. Testing every unit in a layer ensures the correctness of the behavior of such units, specially when being used by other units in the application. This way all units can be reused with confidence.
Now in order to maintain confidence in the Unit being tested, we need to ensure that the tests are reliable and that providence confidence in the correctness of the unit under test. When a test sometimes pass and sometimes fails is called an Erratic Test, and in order to maintain confidence we need to avoid such behavior.
Unit Tests, as explained before, focus on testing the a single unit in a system, unlike integration testing. So it is a best practice to have one database instance per developer or tester. Having two developers running the test fixtures at the same time on the same database create an erratic test behavior, which is not acceptable.
Data-Driven Tests
The pattern we are going to follow in this post is a simple form of the Data-Driven Test Pattern, which is described as:
“We store all the information needed for each test in a data file and write an interpreter that reads the file and executes the tests”.
This pattern is mostly used to avoid code duplication, especially when several test cases just change on different data conditions. This way one test can be executed with several test scripts, instead of writing one test for every data condition.
We’ll use a simple form of the pattern, using Sql syntax for scripts instead of Xml data files. I find it easier to just create an Sql script, execute it and continue with the testing.
Each test must have a context setup. There are several patterns that specify that one test method sets up the data context for the others; for example, one test method tests the insertion of data, while the next test method tests the retrieval of the inserted data. I don’t recommend this setting, this leads to Erratic Tests. Every unit test must be independent of each other. This means that every test method must setup its own environment and it must also clean it up to the initial state.
Unit Testing WCF Services
Unit Testing WCF Services is extremely easy. There are two ways to do this:
1) Include the WCF Library as a reference.
2) Load up the WCF Service host and call the service from the test fixture.
Since we are mostly doing unit testing and not integration testing, loading the WCF Library as a reference works fine. For integration purposes I would write one test fixture for each endpoint in the configuration, but this is out of the scope of this post.
Test Code
So we have two service methods: 1) ProjectService.Insert and 2) ProjectService.GetIdByName. This is the interface of such methods:
namespace WCFTesting
{
using System.ServiceModel;
/// <summary>
/// Project Service Contract.
/// </summary>
[ServiceContract]
public interface IProjectService
{
/// <summary>
/// Inserts a new Project.
/// </summary>
/// <param name="id">Project Identifier.</param>
/// <param name="name">Project Name</param>
/// <param name="description">Project Description</param>
/// <returns>True if successful, false otherwise.</returns>
[OperationContract]
bool Insert(int id, string name, string description);
/// <summary>
/// Returns the id of the project that goes by the selected name.
/// </summary>
/// <param name="name">Project Name</param>
/// <returns><c>int</c></returns>
[OperationContract]
int GetIdByName(string name);
}
}
The service method implementation is shown below:
/// <summary>
/// Inserts a new Project in database.
/// </summary>
/// <param name="id">Project Identifier.</param>
/// <param name="name">Project Name</param>
/// <param name="description">Project Description</param>
/// <returns>True if successful, false otherwise.</returns>
public bool Insert(int id, string name, string description)
{
Database db = DatabaseFactory.CreateDatabase();
DbCommand command = db.GetStoredProcCommand("[dbo].[InsertProject]");
db.AddInParameter(command, "id", DbType.Int32, id);
db.AddInParameter(command, "name", DbType.String, name);
db.AddInParameter(command, "description", DbType.String, description);
db.AddOutParameter(command, "success", DbType.Boolean, 1);
db.ExecuteNonQuery(command);
bool success = (bool) db.GetParameterValue(command, "success");
return success;
}
/// <summary>
/// Returns the id of the project that goes by the selected name.
/// </summary>
/// <param name="name">Project Name</param>
/// <returns><c>int</c></returns>
public int GetIdByName(string name)
{
Database db = DatabaseFactory.CreateDatabase();
DbCommand command = db.GetStoredProcCommand("[dbo].[GetProjectIdByProjectName]");
db.AddInParameter(command, "Name", DbType.String, name);
int id = -1;
using(IDataReader reader = db.ExecuteReader(command)) {
if(reader.Read()) {
id = reader.GetInt32(0);
}
}
return id;
}
Note: All code can be found in the attachment at the end of the post.
As you can see the methods are really simple. We are using a simple call to a stored procedure, getting the results and sending them back to the client.
Now let’s look at the actual unit test fixture:
/// <summary>
/// Test the Service method Insert
/// </summary>
[TestMethod]
public void Insert()
{
using(TransactionScope tranScope = new TransactionScope()) {
int id = 1;
string name = "Project 1";
string description = "Description of Project 1";
Assert.IsTrue(Service.Insert(id, name, description));
Assert.IsTrue(ProjectExists(name, description));
id = 2;
name = "Project 2";
description = "Description of Project 2";
Assert.IsTrue(Service.Insert(id, name, description));
Assert.IsTrue(ProjectExists(name, description));
}
}
/// <summary>
/// Test the Service method GetIdByName
/// </summary>
[TestMethod]
public void GetIdByName()
{
using(TransactionScope tranScope = new TransactionScope()) {
// Insert the Test Data.
SqlHelper.ExecuteSqlScript(Db, @"......UnitTestsScriptsInsertTestProjects.sql");
// Test Service Method.
int id = -1;
string name = "Kook";
id = Service.GetIdByName(name);
Assert.AreEqual<int>(1, id);
name = "Samii";
id = Service.GetIdByName(name);
Assert.AreEqual<int>(2, id);
name = "CPW";
id = Service.GetIdByName(name);
Assert.AreEqual<int>(3, id);
}
}
First we have the insert method, which doesn’t require any existing data, so no script is executed before the service method. We do however wrap everything into a TransactionScope, which ensures that whatever the test does, after the TransactionScope block is out of the scope it will rollback all the changes. I will leave the discussion on Transactions for a later post.
Now, the second method is more interesting. The GetIdByName test method actually needs a setup. We could have created a dependency on the Insert method so that the first test method prepares the data that the GetIdByName method will require to test. But we want to avoid Erratic Test behavior, so we created them completely independent.
The GetIdByName is also wrapped in the TransactionScope so that we can ensure that after the test is done, the data is rolled back to its initial state.
The script (InsertTestProjects.sql) contains three sample projects which the service method will retrieve and we will verify the returned data.
As you can see testing Data-Driven Services is very simple. If you pay close attention to the project you will notice that this way of doing this doesn’t only apply to WCF Services, any .Net assembly can be tested this way.
Hope this helps you on your quest for simplicity and correctness!
Test Solution Requirements
- Visual Studio 2008
- Enterprise Library 4.x
- .Net 3.5
- SQL Server 2005
The Database folder contains the table and stored procedures needed by the code. Just modify the ExecuteScripts.bat to set the database authentication info. Also modify the App.config in the UnitTests project in order to run accordingly.
(Disclaimer: This project has been stripped down so that it is easy enough to understand. This second method, iin order to follow Data-Driven Test, should get the expected data from an Xml file, insert it into the database, and compare accordingly. In this sample we have the data hard coded for simplicity. Building an interpreter is our of the scope of this post.)
* References:
- Meszaros, Gerard. “xUnit Test Patterns: Refactoring Test Code”
2007, Pearson Education.
Amazon
Let the Clouds Make your life easier…
// March 24th, 2009 // No Comments » // cloud computing, fun
I just stumbled upon this great link that explains the power of the clouds for software solutions and how it reduces complexity: Here
Remove files recursively..
// March 10th, 2009 // No Comments » // Source Control, powershell
I had a problem a couple of weeks ago, when my main Subversion repository completely died out of data corruption. I was trying to check-in my latest changes, but I just couldn’t. Nothing was lost since I do regular backups of my repositories. So I was in good shape. I thought to myself this was the best chance to migrate to TFS, which I have been wanting to do for a while.
Note: I did not leave subversion in favor of TFS because of this corruption. This data corruption was expected to happen because the machine usually gets killed in the middle of backup or by the occasional “Windows Update”; so the repository was destined to die eventually. I could have fixed the repository in no time with the tools that Subversion provides or simply by restoring backups. But I moved to TFS mainly because of the project integration in all aspects and not only source control, and because most of my clients use TFS, so integration with their systems is also easier.
Anyways I needed a clean copy of my newest changes so that I could import it into TFS. I felt lazy at the moment and I chose the complex solution, clean up my subversion repository copy. My project has a LOT of folders, so deleting the .svn folders became a HUGE effort. I decided to use a simple shell command to do that, like I just to do in linux:
rm -rf `find . -type d -name .svn`
So I started looking on google to see what was the way to it in Powershell and I found really complex solutions like:
$fso = New-Object -com "Scripting.FileSystemObject";
$folder = $fso.GetFolder("C:\\Test\\");
foreach ($subfolder in $folder.SubFolders) {
if ($subfolder.Name -like "*.svn"){
remove-item $subfolder.Path -Verbose
}
}
Source: Here
It really scared me! I thought that, if that was the easiest way to delete recursively, then powershell is doomed. Thanks to google, I did find a simpler way to do this:
dir . -recurse .svn -fo | remove-item -force
Which is quite elegant and fast! Sometimes I just don’t understand why it is so difficult to come up with the simple answer. It happens to me quite often. It is extremely easy to come up with a complex solution…but to actually have a simple solution is always difficult. This is only one example.
Anyways this did the trick and it works perfectly.
[Update]: I forgot to add the ‘-fo’ option which shows the hidden files (in this case the .svn folders). Otherwise this would not work.
Sticky Sorter
// November 20th, 2008 // 2 Comments » // microsoft, scrum
Microsoft just announced a very cool Research project called ‘Sticky Sorter‘ which is a tool that helps us organize information using sticker notes or post-its.
From the website:
StickySorter is an Office Labs sponsored spare-time project by two Microsoft employees, Julie and Sumit. The idea sprung from the need for project teams all over the world to gather and organize data using a collaborative process known as affinity diagramming. Since its inception, StickySorter has evolved into a desktop application so anyone can use it to collaborate and organize ideas electronically, using a familiar sticky note interface.
What I see here is something that I have been looking for some time now and which is specially useful for Scrum. This can be used to recreate the Scrum sprint backlog in a very friendly way.
I have created a sample of what it would look like using the tool:
I need to play with it a bit more in order to see it’s full capabilities, and try to apply it to scrum. You can download the tool here.
Alchemy….
// November 20th, 2008 // No Comments » // .net, RIA, c++
I have not really been a follower of Macromedia (now part of Adobe) or its products; specially Flash, but I just found out about one research project that does capture my attention: Alchemy.
From the press release:
Alchemy is a research project that allows users to compile C and C++ code that is targeted to run on the open source ActionScript Virtual Machine (AVM2). The purpose of this preview is to assess the level of community interest in reusing existing C and C++ libraries in Web applications that run on Adobe® Flash® Player and Adobe AIR®.
This project promises that C/C++ libraries that have no OS dependencies can be run on the Adobe AIR platform. This is HUGE. Just to think that at least 90% of my libraries can be used in Web Applications is awesome.
A not so direct competitor, Microsoft’s Silverlight, does provide a way to reuse C++ libraries via C++/CLI, and it works like a charm; I happend to have a lot of C++ libraries which have valuable code. Lately I have been reusing those libraries in Web Applications via C++/CLI and WebServices. It works, and it works fine.
I have not worked with Silverlight 2.0 yet; I have played around with it, but I have not done anything that is worth mentioning. In my tests, I see Ican also reuse those C++ libraries with C++/CLI and Webservices. The problem is that this approach will only work on Windows, since C++/CLI is not supported by Mono.
Another approach would be to make the WebServices in native C++, and call it from anywhere: Silverlight, Javascript and .Net. This would work anywhere.
This doesn’t take away the credit for Alchemy, which makes the C++ libraries natively accessible to Adobe AIR applications, in a way this is very close to what C++/CLI does.
The purpose of the Alchemy project is :
Alchemy is primarily intended to be used with C/C++ libraries that have few operating system dependencies. Ideally suited for computation-intensive use cases, such as audio/video transcoding, data manipulation, XML parsing, cryptographic functions or physics simulation, performance can be considerably faster than ActionScript 3.0 and anywhere from 2-10x slower than native C/C++ code. Alchemy is not intended for general development of SWF applications using C/C++.
Comparing it with C++/CLI, I do see an advatage from using C++/CLI to reuse C++ libraries in RIA applications over the Alchemy project: I can reuse .Net libraries with C++ native code, which gives me the best of both worlds.
I did some research on Alchemy, and it seems it doesn’t allow Flex code to be embedded with C++ native code. My research was not very comprehensive to say the least, so I could be wrong. It could also be too soon to tell since this is still in early stages of research and development.
In conclusion, this project seems very interesting, and I’m going to keep an eye out for it.
