[Java 8] Generate many stubs for any class

Product.java

import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Product {

    private final long id;
    private final String description;

    private Product(long id, String description) {
        this.id = id;
        this.description = description;
    }

    private static Product of(long id, String description) {
        return new Product(id, description);
    }
    
    public static Product notebook() {
        return Product.of(1, "Phone");
    }

    public static Product mouse() {
        return Product.of(2, "Notebook");
    }

    public static Product keyboard() {
        return Product.of(3, "Notebook");
    }
  
    public static List<Product> many(int size, Supplier<Product> method) {
        return IntStream.range(1, ++size)
            .mapToObj(x -> method.get())
            .collect(Collectors.toList());
    }
}

Test.java

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class Test {

    @Test
    public static void generate() {

        List<Product> products = Stream.of(
                Product.many(5, Product::keyboard),
                Product.many(4, Product::mouse)
            )
            .flatMap(List::stream)
            .collect(Collectors.toList());
            
        assertEquals(9, products.size());
    }
}