I'm writing unit tests for a controller in an MVC3 web project, but my tests throw exceptions when they try and access a resource like this:
return Index(Resources.Strings.MyStringResource);
The resource is a .resx file titled Strings.
I'm using the Moq libraries to achieve unit test for HttpContextBase functionality, so I was wondering how I would go about using the Moq libraries to access an App_GlobalResource.
Any help or pointers would be greatly appreciated!
You can't, at least not directly. The strongly-typed classes that are generated from resource (.resx) files expose static, not instance methods.
Because of this, they can't implement an interface method, nor are they virtual; Moq requires that at least one of these conditions are met in order to create a mock.
To get around this, you would create an abstraction, like anything else:
public interface IResources
{
string MyStringResource { get; }
}
You'd pass (or inject) an implementation of this into your controller, and then pass that to your Index method. That implementation might look something like this:
public class ResourcesWrapper : IResources
{
public string MyStringResource
{
get
{
return Resources.Strings.MyStringResource;
}
}
}
Then, when you're testing, you can use Moq to create a mock of the IResources interface, and pass that to your controller, like so:
// Create the mock.
var mock = new Mock<IResources>();
// Setup the property.
mock.SetupProperty(m => m.MyStringResource, "My Mocked Value");
// Pass the object somewhere for use.
Assert.AreEqual(mock.Object.MyStringResource, "My Mocked Value");
So, after implementing casperOne's answer, I ran into another error:
I was presented with an IOException stating:
"Could not load file or assembly 'App_GlobalResources' or one of its dependencies. The system cannot find the file specified.":"App_GlobalResources"
Scott Allen provided the reason and inherent solution to this problem.
So what I did was made a new resources file in a new folder named 'TResources' in my web project, named 'TResources' purely because it is a Resources folder that is only being created and used for Testing purposes (clever, eh?)
I then changed the properties of my ResourcesWrapper class to return TResources.Strings.MyStringResource rather than Resources.Strings.MyStringResource.
NOTE: The properties in the IResources interface must not be read-only, as when setting up the mock object, if the property is read-only it will fail as the value cannot be set.
Therefore, IResources should look a little something like this:
public interface IResources
{
string MyStringResource { get; set; }
}
ResourcesWrapper should then implement IResources like this:
public class ResourcesWrapper : IResources
{
public string MyStringResource
{
get
{
return TResources.Strings.MyStringResource;
}
set
{
//do nothing
}
}
}
So that you can then achieve a successful mock in your Unit Test, like this:
var mock = new Mock<IResources>();
mock.SetupProperty(m => m.MyStringResource, "");
NOTE: You don't have to specify anything in the initialValue parameter of the method above, as the property will be returning a value retrieved from the Strings.resx.
That concludes my question, I hope this can be helpful to someone else on internet land!
This response to a similar Stack Overflow question by Darin Dimitrov provides a much simpler approach. It's all about modifying the Resources.resx file properties to support unit testing.
