Execute unit tests serially (rather than in parallel)

Question

I am attempting to unit test a WCF host management engine that I have written. The engine basically creates ServiceHost instances on the fly based on configuration. This allows us to dynamically reconfigure which services are available without having to bring all of them down and restart them whenever a new service is added or an old one is removed.

I have run into a difficulty in unit testing this host management engine, however, due to the way ServiceHost works. If a ServiceHost has already been created, opened, and not yet closed for a particular endpoint, another ServiceHost for the same endpoint can not be created, resulting in an exception. Because of the fact that modern unit testing platforms parallelize their test execution, I have no effective way to unit test this piece of code.

I have used xUnit.NET, hoping that because of its extensibility, I could find a way to force it to run the tests serially. However, I have not had any luck. I am hoping that someone here on SO has encountered a similar issue and knows how to get unit tests to run serially.

NOTE: ServiceHost is a WCF class, written by Microsoft. I don't have the ability to change it's behavior. Hosting each service endpoint only once is also the proper behavior...however, it is not particularly conducive to unit testing.

Answer 1

I don't know the details, but it sounds like you might be trying to do integration testing rather than unit testing. If you could isolate the dependency on ServiceHost, that would likely make your testing easier (and faster). So (for instance) you might test the following independently:

• Configuration reading class
• ServiceHost factory (possibly as an integrtion test)
• Engine class that takes an IServiceHostFactory and an IConfiguration

Tools that would help include isolation (mocking) frameworks and (optionally) IoC container frameworks. See:

• http://www.mockobjects.com/
• http://www.hanselman.com/blog/ListOfNETDependencyInjectionContainersIOC.aspx

Answer 2

Maybe you can use Advanced Unit Testing. It allows you to define the sequence in which you run the test. So you may have to create a new cs file to host those tests.

Here's how you can bend the test methods to work in the sequence you want.

[Test]
[Sequence(16)]
[Requires("POConstructor")]
[Requires("WorkOrderConstructor")]
public void ClosePO()
{
  po.Close();

  // one charge slip should be added to both work orders

  Assertion.Assert(wo1.ChargeSlipCount==1,
    "First work order: ChargeSlipCount not 1.");
  Assertion.Assert(wo2.ChargeSlipCount==1,
    "Second work order: ChargeSlipCount not 1.");
  ...
}

Do let me know whether it works.

Answer 3

See this post