How To Mock Method Of A Class Under Test With MOQ

I have a service class that i want to unit test. The service calls a repository class method in order to save some data. But before I call the save method, I have a validate method that belongs to the service class under test which validates the properies of the class to be persisted as a parameter to the repository save method.I know that to verify that the repository save method is called, i have to mock the repository class and set up the save method, but how do i verify that the validate method belonging to the service class under test is called when unit testing the method under test since they belong to the same class?