How do I get Assembly name from full assembly string?

I have a string like this:

"MyProduct.Framework.Business.ShopBusiness"

But the assembly name it self is only:

"MyProduct.Framework.Business"

I need to create a string like this:

"MyProduct.Framework.Business.ShopBusiness, MyProduct.Framework.Business"

Because I'm trying to solve this problem: http://ift.tt/1ZLLgCB

So basically I have this:

Type executingClass = Type.GetType(TestContext.FullyQualifiedTestClassName);

And I need something like this:

Type executingClass = Type.GetType(TestContext.FullyQualifiedTestClassName + ", " + Assembly.FromString(TestContext.FullyQualifiedTestClassName));

Is there any built-in method as I invented "Assembly.FromString()" above?

I know it's not difficult to create one, but I would like to know if this method already exists.