IDependencyResolver in Moq Test

Question

The below code is part of a solution that is being migrated from asp.net to .netcore and some of the tests are still in asp.net. From what I know is that in .netcore there is no use of DependenceyResolver because we use Microsofts inbuilt Dependency Injection mechanism for injecting Dependencies.

Hence based upon this I have two questions:

1. What I wanted to know is below the correct way to dependency inject in a Moq test ASSUMING that the persons code is in asp.net.
2. If the below code is not what I said in the 1st point then what is trying to be achieved below?

Thanks Any extra information will also be widely appreciated.

[TestInitialize]
public void Initialise()
{
  DependencyResolverSetup();
}

 private void DependencyResolverSetup()
 {
     pizzaAvailibiltyMock = new Mock<IPizzaAvailibiltyMock>();
     pizzaClientOrchestrationMock = new Mock<IPizzaClientOrchestrationMock>();
     Mock<IDependencyResolver> dr = new Mock<IDependencyResolver>();
     dr.Setup(x => x.GetService(typeof(IPizzaAvailibiltyMock))).Returns(pizzaAvailibiltyMock.Object);
     dr.Setup(x => x.GetService(typeof(IPizzaClientOrchestrationMock))).Returns(pizzaClientOrchestrationMock.Object);
     DependencyResolver.SetResolver(dr.Object);
 }

I tried to remove the above code from the test and I can see no apparent errors