如何将项目添加到模拟DbSet(使用Moq) [英] How to add an item to a Mock DbSet (using Moq)

问题描述

我正尝试建立一个模拟DbSet进行测试.我在这里使用了该教程， http://www.loganfranken.com/blog/517 /mocking-dbset-queries-in-ef6/并稍加修改，以便每次调用GetEnumerator都会返回一个新的枚举数(我遇到的另一个问题).但是，我在将项目添加到DbSet时遇到困难.

I'm trying to set up a mock DbSet for testing purposes. I used the tutorial here, http://www.loganfranken.com/blog/517/mocking-dbset-queries-in-ef6/ and slightly modified it so calling GetEnumerator returns a new enumerator each time (another problem i was having). However, I am having difficulty adding items to the DbSet.

输出结果是preCount = 3 postCount =3.但是，我希望它是precount = 3 postCount = 4.

The output is preCount = 3 postCount = 3. However, I expect it to be precount = 3 postCount = 4. Any help is greatly appreciated.

static void Main(string[] args)
    {
        Debug.WriteLine("hello debug");

        List<string> stringList = new List<string>
        {
            "a", "b", "c"
        };

        DbSet<string> myDbSet = GetQueryableMockDbSet(stringList);
        int preCount = myDbSet.Count();
        myDbSet.Add("d");
        int postCount = myDbSet.Count();
        Debug.WriteLine("preCount = " + preCount + " postCount = " + postCount);
    }

    private static DbSet<T> GetQueryableMockDbSet<T>(List<T> sourceList) where T : class
    {
        var queryable = sourceList.AsQueryable();

        var dbSet = new Mock<DbSet<T>>();
        dbSet.As<IQueryable<T>>().Setup(m => m.Provider).Returns(queryable.Provider);
        dbSet.As<IQueryable<T>>().Setup(m => m.Expression).Returns(queryable.Expression);
        dbSet.As<IQueryable<T>>().Setup(m => m.ElementType).Returns(queryable.ElementType);
        dbSet.As<IQueryable<T>>().Setup(m => m.GetEnumerator()).Returns(() => queryable.GetEnumerator());

        return dbSet.Object;
    }

推荐答案

myDbSet不是DbSet的真正实现，而是一个模拟，这意味着它是 fake ，需要为所有设置您需要的方法. Add也不例外，因此需要对其进行设置以执行您需要的操作，否则它什么也不做.

myDbSet is not real implementation of DbSet but a mock which means it's fake and it needs to be setup for all methods you need. The Add is not exception so it needs to be set up to do what you need otherwise it does nothing.

添加如下内容，并在调用myDbSet.Add("d");时将'd'添加到列表中，以后可以返回.

Add something like the following and when the myDbSet.Add("d"); is called then the 'd' is added to the list and can be returned later.

dbSet.Setup(d => d.Add(It.IsAny<T>())).Callback<T>((s) => sourceList.Add(s));

完整代码

private static DbSet<T> GetQueryableMockDbSet<T>(List<T> sourceList) where T : class
{
    var queryable = sourceList.AsQueryable();

    var dbSet = new Mock<DbSet<T>>();
    dbSet.As<IQueryable<T>>().Setup(m => m.Provider).Returns(queryable.Provider);
    dbSet.As<IQueryable<T>>().Setup(m => m.Expression).Returns(queryable.Expression);
    dbSet.As<IQueryable<T>>().Setup(m => m.ElementType).Returns(queryable.ElementType);
    dbSet.As<IQueryable<T>>().Setup(m => m.GetEnumerator()).Returns(() => queryable.GetEnumerator());
    dbSet.Setup(d => d.Add(It.IsAny<T>())).Callback<T>((s) => sourceList.Add(s));

    return dbSet.Object;
}

输出

hello debug
preCount = 3 postCount = 4

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