From empirical evidence, we know that improving code coverage by verifying all the boundary conditions, and ensuring quality of code-base significantly enhances maintainability and comprehensibility of complex software systems. Therefore, writing effective unit and integration tests has become one of the integral part in software development life cycle. In fact, development methodology such as TDD has been embraced rapidly due to these realized benefits.
In today’s post, we talk more about TestContext of mstest. In particular, we focus on its usage in devising effective unit tests. Before moving forward, we would like to outline the previous posts of the series regarding Unit Testing.
What is TestContext?
TestContext is an abstract class of Microsoft.VisualStudio.TestTools.UnitTesting namespace. It exposed several properties related to the current context (i.e., current test run). In addition, it provides following supports:
- Get/set context-sensitive properties and instances, For instance,
- During Asp.net unit tests, it stores server’s URL, and Page object.
- For data driven unit tests, it provides access to the data rows.
- Mechanism to measure performance of unit tests.
Following is the class definition of the TestContext class.
| public abstract class TestContext | |
| { | |
| public const string AspNetDevelopmentServerPrefix = "AspNetDevelopmentServer."; | |
| protected TestContext(); | |
| public virtual UnitTestOutcome CurrentTestOutcome { get; } | |
| public abstract DbConnection DataConnection { get; } | |
| public abstract DataRow DataRow { get; } | |
| public abstract IDictionary Properties { get; } | |
| public virtual System.Web.UI.Page RequestedPage { get; } | |
| public virtual string TestDeploymentDir { get; } | |
| public virtual string TestDir { get; } | |
| public virtual string TestLogsDir { get; } | |
| public virtual string TestName { get; } | |
| public abstract void AddResultFile(string fileName); | |
| public abstract void BeginTimer(string timerName); | |
| public abstract void EndTimer(string timerName); | |
| public abstract void WriteLine(string format, params object[] args); | |
| } |
How can we initialize TestContext?
To start using TestContext, we need to add a property in our unit test class, e.g., UserManagerTests, as illustrated below.
As we run a unit test defined in UserManagerTests, we automatically get an instance of TestContext with the relevant properties configured according to the current context. Thus, we do not require to explicitly instantiate it. Using debug mode, we can verify that the instance of TestContext is an instance of UnitTestAdapterContext, which is, in fact, derived from TestContext abstract class.
In addition, Microsoft.VisualStudio.QualityTools.Tips.UnitTest.Adapter.dll assembly contains UnitTestAdapterContext class, which is located in the directory of private assemblies installed in <vs installation directory>\common7\IDE\PrivateAssemblies.
Note that the property TestContext is actually initialized after ClassInitialize and before TestInitialize gets invoked.
In this post, we discuss how we can initialize TestContext in a test class. As a continuation of this discussion, we outline several use-cases of TestContext in the following posts.
- Getting Directory of Current Context with TestContext.
- Performance Measurement with TestContext.
- Output Additional Information with TestContext.
- Unit Testing in ASP.NET Context with TestContext.
- TestContext in Data Driven Unit Tests.
- Add Result File with TestContext.
Conclusion
To sum up, in this series, we introduce TestContext and has discussed how we can utilize it in different scenarios to write effective unit and integration tests. We hope that it would help to devise more effective and maintainable unit tests. Lastly, we emphasize on designing test cases thoroughly, and mapping them essentially into unit and integration tests accordingly, because only "harnessing the power that is provided by the tool and utilizing it effectively and every possible way" could bring desirable result. We highly appreciate any comments or any suggestion regarding this series. Thanks.
Revisions
[R-1: 04-04-2013] Porting this blog-post from its weblogs.asp.net page.
adilakhter λ 
It is a little hard to see what you mean, by refering to images which is no longer there
Indeed! I will try to restore the missing images. Sorry for the inconvenience.
I’m pretty new to Unit Testing and I see this in the code I’m looking at:
private TestContext testContextInstance;
public TestContext TestContext
{
get
{
return testContextInstance;
}
set
{
testContextInstance = value;
}
textContextInstance is null until set to value. DataConnection property remains null, but testContextInstance still gets populated. Where does the data come from? I know it’s using a data source somewhere and probably running a query, but how can you tell where these are?
Thanks,
Rich
My mistake…I totally overlooked the DataSource Decorator on the TestMethod. It’s pointing to a .csv file. At least now it’s making a lot more sense to me. It was also good to see the class definition of TestContext. Now, it’s all clear. Thanks.