…nterface.

How to use:
var substitute = Substitute.ForPartsOf<ISomeInterface,SomeImplementation>(argsList);

In this case, it doesn't matter if methods are virtual or not; it will intercept all calls since we will be working with an interface all the time.

Limitations:

Overriding virtual methods effectively replaces its implementation both for internal and external calls. With this implementation Nsubstitute will only intercept calls made by client classes using the interface. Calls made from inside the object itself to it's own method, will hit the actual implementation.

…ods or sealed classes implementing an interface.

How to use:
var substitute = Substitute.ForTypeForwardingTo <ISomeInterface,SomeImplementation>(argsList);

In this case, it doesn't matter if methods are virtual or not; it will intercept all calls since we will be working with an interface all the time.
For
Limitations:

Overriding virtual methods effectively replaces its implementation both for internal and external calls. With this implementation Nsubstitute will only intercept calls made by client classes using the interface. Calls made from inside the object itself to it's own method, will hit the actual implementation.