public async Task AddOrUpdatePerson_CallsAddOrUpdateFromDbSet()
{
// Arrange
var mockSet = NSubstituteUtils.CreateMockDbSet <Person>();
var mockContext = Substitute.For <IPeopleDbContext>();
mockContext.People.Returns(mockSet);
var service = new PeopleService(mockContext);
// Act
await service.AddOrUpdatePerson(new Person { FirstName = "John", LastName = "Doe" });
// Assert
// verify that DbSet.AddOrUpdate has been called once
mockSet.Received(1).AddOrUpdate(Arg.Any <Person>());
await mockContext.Received(1).SaveChangesAsync();
}