如何编写紧耦合的工厂设计模式代码块的Xunit测试用例？

// 产品接口
public interface IProduct
{
    void Use();
}

// 具体产品A
public class ConcreteProductA : IProduct
{
    public void Use()
    {
        Console.WriteLine("Using ConcreteProductA");
    }
}

// 具体产品B
public class ConcreteProductB : IProduct
{
    public void Use()
    {
        Console.WriteLine("Using ConcreteProductB");
    }
}

// 工厂类
public class ProductFactory
{
    public IProduct CreateProduct(string type)
    {
        switch (type)
        {
            case "A":
                return new ConcreteProductA();
            case "B":
                return new ConcreteProductB();
            default:
                throw new ArgumentException("Invalid product type");
        }
    }
}

using Xunit;

public class ProductFactoryTests
{
    [Fact]
    public void CreateProduct_ShouldReturnConcreteProductA_WhenTypeIsA()
    {
        // Arrange
        var factory = new ProductFactory();

        // Act
        var product = factory.CreateProduct("A");

        // Assert
        Assert.IsType<ConcreteProductA>(product);
        ((ConcreteProductA)product).Use();
    }

    [Fact]
    public void CreateProduct_ShouldReturnConcreteProductB_WhenTypeIsB()
    {
        // Arrange
        var factory = new ProductFactory();

        // Act
        var product = factory.CreateProduct("B");

        // Assert
        Assert.IsType<ConcreteProductB>(product);
        ((ConcreteProductB)product).Use();
    }

    [Fact]
    public void CreateProduct_ShouldThrowArgumentException_WhenTypeIsInvalid()
    {
        // Arrange
        var factory = new ProductFactory();

        // Act & Assert
        Assert.Throws<ArgumentException>(() => factory.CreateProduct("C"));
    }
}