[开发测试]C#---单元测试

假设场景

电扇依赖于电源，电源电流值不同电扇工作效果不同

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var power = new PowerSupply();
            var fan = new DeskFan(power);
            Console.WriteLine(fan.Work());
        }			
    }
    class PowerSupply
    {
        public int GetPower()
        {
            return 210;
        }
    }
    class DeskFan
    {
        private PowerSupply _powerSupply;
        public DeskFan(PowerSupply powerSupply)
        {
            _powerSupply = powerSupply;
        }
        public string Work()
        {
            int power = _powerSupply.GetPower();
            if (power <= 0)
            {
                return "Won't Work";
            }
            else if (power < 100)
            {
                return "Slow";
            }
            else if (power < 200)
            {
                return "Work fine";
            }
            else
            {
                return "Warning!";
            }
        }
    }
}

可以看出，此时如果想测试风扇的工作情况，就必须去PowerSupply类内部提供电源的方法中去修改代码，而一个类设计好之后不应该再去修改代码的。就比如说这个场景下不止是风扇连接着电池，而还有设备也连接着。为了测试风扇而更改代码很可能会导致其他设备出故障。

引入接口，进行解耦，再使用单元测试

为了解决上面的测试问题，我们抽象出了一个电源提供接口，写一个测试类实现电源提供接口，专门用来测试电源电力大小对风扇造成的影响：

namespace TestClass
{
    class Program
    {
        static void Main(string[] args)
        {
            var fan = new DeskFan(new TestPowerSupply());
            fan.Work();
            Console.ReadKey();
        }
    }
    public  interface IPowerSupply
    {
        int GetPower();
    }

    /// <summary>
    /// 电源供应类
    /// </summary>
    public class PowerSupply:IPowerSupply
    {
        public int GetPower()
        {
            return 100;
        }
    }
    /// <summary>
    /// 测试电流
    /// </summary>
    public class TestPowerSupply : IPowerSupply
    {
        public int GetPower()
        {
            return 100000;
        }
    }
    /// <summary>
    /// 电扇
    /// </summary>
    public class DeskFan
    {
        private IPowerSupply _powerSupply;
        public DeskFan(IPowerSupply powerSupply)
        {
            _powerSupply = powerSupply;
        }
        /// <summary>
        /// 运行，还要验证电流力度
        /// </summary>
        /// <returns></returns>
        public string Work()
        {
            int power = _powerSupply.GetPower();
            //简单判断一下
            if(power<=0)
            {
                return "Wont't work";
            }
            else
            {
                return "Working";
            }

        }
    } 
}

要测试的话，我们可以使用单元测试进行调试。新建一个单元测试

namespace TestClassTests
{
    public class UnitTest1
    {
        [Fact]
        public void PowerLowerThanZero_OK()
        {
            var mock = new Mock<IPowerSupply>();
            mock.Setup(s=>s.GetPower()).Returns(()=>0); 
            var fan = new DeskFan(new PowerSupplyThanZero(0));
           var test= fan.Work();
            Assert.Equal("",test);

            //第二种写法，引用Moq.dll。此时就不需要再实现接口了，直接填需要的值
            var mock = new Mock<IPowerSupply>();
            mock.Setup(s => s.GetPower()).Returns(() => 0);

            var fan = new DeskFan(mock.Object);
            var test = fan.Work();
            Assert.Equal("", test);


        }
    } 
    public class PowerSupplyThanZero : IPowerSupply
    {
        private int _power;
        public PowerSupplyThanZero(int power)
        {
            _power = power;
        }
        public int GetPower()
        {
            return _power;
        }
    }
}

这样的测试方法进很正规了，不会影响到其他模块。