TypeDescriptor.AddAttributes(testType, new ProviderTestAttribute());
var registeredAttributeTypes = TypeDescriptor.GetAttributes(testType).Cast<Attribute>().Select(attr => attr.GetType()).ToArray();
Assert.AreEqual(2, registeredAttributeTypes.Length);
TypeDescriptor.AddAttributes(testType, new ProviderTestAttribute());
var registeredAttributeTypes = TypeDescriptor.GetAttributes(testType).Cast<Attribute>().Select(attr => attr.GetType()).ToArray();
Assert.AreEqual(2, registeredAttributeTypes.Length);