MockMe is a library for mocking dependencies in your production code. Unlike other libraries that can only mock interfaces and virtual methods, MockMe can mock sealed classes and non-virtual methods.
Download NuGet package, then the source generators and the "MockMe.Mock" type will be available in your project.
var mock = Mock.Me<MyRepo>();
mock.Setup.ExpensiveDatabaseCall().Returns(99);
MyRepo myRepo = mock.MockedObject;
Assert.Equal(99, myRepo.ExpensiveDatabaseCall());
mock.Assert.ExpensiveDatabaseCall().WasCalled();
Check out the Wiki for more examples.