public async Task InsertRandomData()
        {
            //Arrange
            var dbSet   = Substitute.For <DbSet <DefaultModel> >();
            var context = Substitute.For <DefaultContext>();

            context.DefaultModels = dbSet;

            var controller = new DefaultController(context);

            //Act
            await controller.GenerateData();

            //Assert
            dbSet.Received(1).Add(Arg.Any <DefaultModel>());
            await context.Received(1).SaveChangesAsync();
        }