How to mock Application.Current for unit-testing?

Question

I have this:

<Image.Effect>
    <fx:GrayscaleEffect DesaturationFactor="0"/>
</Image.Effect>

and this:

public class GrayscaleEffect : ShaderEffect{
    private static PixelShader _pixelShader = new PixelShader()
        {
            UriSource = new Uri(@"pack://application:,,,/Effects/GrayscaleEffect.ps")
        };
    /* ... rest of the class ... */
}

When I unit-test it (MSTest), it obviously raises IOException (since Application.Current is null, so pack://application:,,,/... points to nowhere) with this error:

Assembly.GetEntryAssembly() returns null. Set the Application.ResourceAssembly property or use the pack://application:,,,/assemblyname;component/ syntax to specify the assembly to load the resource from.

How do I mock/inject whatever needed to resolve it ?

Answer 1

Tal's answer didnt work for me, I am just calling below before running my test and Application.Current is populated:

var app = new Application();