Automating a WCF Service Test using VSTS

I needed to veer off from testing our website UI using webtests to testing the service layer of our website. My client company has standardized on Visual Studio 2010/2012 for our test harness.

I had a couple of options: use the unit test framework or the webtest format, a declarative XML style. I’ll outline my thought process here, with credit to other sources including the VSTS Forum where this decision is discussed: Issue with VSTS webtest on WCF Servce.

I already have a bunch of test cases coded in the webtest format that I run using a custom test launcher and preferred to stick with the webtest style if possible.

The developer of the service expressed some concern about whether the webtest would be a good method of testing his new service, as he was most familiar with creating a service proxy and testing the WCF service by exercising properties and methods from that. He wanted me to evaluate calling the web methods from a VSTS webtest vs. a unit test by watching the http traffic using the Fiddler tool to make sure the service would be called in the same manner.

Fiddler Web Debugging Tool

Sure enough, my test harness proved that it didn’t matter whether I called the web service from a web test or a unit test, the http traffic recorded by Fiddler was identical. So for me, it was a no-brainer, I’d create the tests using the webtest format. If I had to summarize the pros and cons, it would go something like this:

Automating a WCF Service test

Unit Test Format
Pros

• Easier to call the service after creating a web service proxy class
• Neater, cleaner code when setting properties and calling methods of the proxy object

Cons

• The service endpoint is written into a config file and is more work to parameterize.
• The test project is compiled to a DLL unlike the declarative XML format of the webtest.

Webtest Format (pretty much the opposite of the above)
Pros

• The test format is a readable declarative XML file format.
• You can record a call to the WCF service using the wcftestclient.exe tool from VSTS, record the call in the Fiddler tool, and save the session in .webtest format very quickly.
• It is very easy to parameterize any part of the service request URI, string body, and header using the concept of VSTS context name-value parameters.

Cons

• Creating validation code may require you create a custom validation rule class to perform detailed validation of the service response packet.

It was the final point in favor of the webtest format that won me over -- we can easily point our service to a dev, test, stage, or prod environment, or change the input parameters on the method by changing some context paramter values from our custom test framework.