Monday, 10 December 2012

Testing an WCF Rest Service directly and via a local instance created by WebServiceHost

Here is an example of a simple REST based WebService which is tested using 3 techniques:

  • IIS
  • Direct object creation
  • Locally hosted instance of the WCF service (using .Net's WebServiceHost class)


It all starts with an Interface definition:

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Which is implemented by

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Testing Version method using IIS/Cassini

To access this Service in IIS/Cassini, we call the SetRouteTable method from the Global.asax.cs Application_Start callback:

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Which sets the AdminRest as the route (i.e. url path) into the Admin_REST service

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Since we have the help pages enabled (on web.config)

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We can view a wsdl-type-helper page at http://localhost:3187/AdminREST/help

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And invoke the Version method using http://localhost:3187/AdminREST/Version

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Testing Version method directly

Inside a VisualStudio 2010 Test Project: image lets add a test that creates an instance of the AdminRest class and invokes it directly (note that this technique will not work for tests that require live (or configured) Asp.NET Http objects)

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When executed image the UnitTest should succeed and show the version number in its Output window:

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Testing Version method using a WCF Host

A more interesting/powerful technique to host the WCF service temporarily on a local port, and access the service via HTTP.

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The code above is used by this Unit Test that opens and closes the WCF port during its execution:

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Here is the output of the the CheckWebServicesHost test:

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To make this work (and to help debugging) I added/used the DNS entry local (instead of localhost) , which allowed me to view the WCF traffic in Fiddler:

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Note that the local DNS mapping needs to defined in the system32/etc/hosts file:

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Another change that I had to do, was to give my current user account, the ability to bind to the 20000 port.

This was done using the HttpNamespaceManager.zip tool available from the AddressAccessDeniedException: HTTP could not register URL http://+:8080/<…> MSDN Article.


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Here are couple posts that explain why this last step was required:
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