单元测试 mock EF 中DbContext 和DbSet Include

现

现在EF越来越流行了，很多时候业务成都是直接访问DbContext 和DbSet来操作数据的。 那么我们测试的时候如何来mock这2个对象了？现在时间很晚了， 就直接贴code吧

首先看看的我们DbContext的类吧：

public class BloggerEntities : DbContext
{
public BloggerEntities()
: base("BloggerEntities")
{
Configuration.ProxyCreationEnabled = false;
}

public virtual DbSet<Blog> Blogs { get; set; }
public virtual DbSet<Article> Articles { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new ArticleConfiguration());
modelBuilder.Configurations.Add(new BlogConfiguration());
}
}

public virtual DbSet<Blog> Blogs { get; set; }

public virtual DbSet<Article> Articles { get; set; }

注意了，我一般DbSet属性是没有添加virtual， 结果上面的 mockedContext.Setup(lambdaExpression).Returns(method.Invoke(null, new[] { listForFakeTable }));这句一直报错，搞了我2个小时都没有搞定。不能mock 实例方法。

单元测试code：

static void Main(string[] args)
{
var context = EntityFrameworkMockHelper.GetMockContext<BloggerEntities>().Object;
context.Articles.Add(new Article
{
Author = "Gavin",
BlogID = 1,
Contents = "test",
ID = 2,
Title = "test title",
URL = "article URL"
});
List<Blog> blogs = new List<Blog> {
new Blog
{
ID = 1,
URL = "blog url",
Name = "blogs name"
},
new Blog
{
ID = 1,
URL = "blog url",
Name = "blogs name2222"
}
};
context.Articles.First().Blog = blogs[0];

//add
context.Blogs.AddRange(blogs);
//query
var query1 = (from a in context.Articles
join b in context.Blogs on a.BlogID equals b.ID
select new { Author = a.Author, BlogName = b.Name }).ToList();
//remove
var blog = context.Blogs.FirstOrDefault(x => x.Name == "blogs name2222");
context.Blogs.Remove(blog);
//update
context.Articles.FirstOrDefault(x=>x.ID==2).URL = "updated url";
var query2 = (from a in context.Articles
join b in context.Blogs on a.BlogID equals b.ID
select new { Author = a.Author, ArticleUrl = a.URL }).ToList();

EFService service = new EFService(context);
var includetest1 = service.GetArticles();
var includetest2 = service.GetArticles2();
var includetest3 = service.GetArticles3();
}

  注意为了 测试include 这里我单独写了一个 service

public class EFService
{
BloggerEntities DBContext { set; get; }
public EFService(BloggerEntities ctx)
{
DBContext = ctx;
}
public List<Article> GetArticles()
{
return DBContext.Articles.Include("Blog").ToList();
}
public List<Article> GetArticles2()
{
return DBContext.Articles.Include(x=>x.Blog).ToList();
}
public List<Article> GetArticles3()
{
return (from a in DBContext.Articles select a).Include(x => x.Blog).ToList();
}
}

我这里的EFService 和BloggerEntities在同一个 程序集里面， 实际上我们应该分开的。

EntityFrameworkMockHelper 的实现如下：

public class MockedDbContext<T> : Mock<T> where T : DbContext
{
public Dictionary<string, object> Tables
{
get { return _Tables ?? (_Tables = new Dictionary<string, object>()); }
}
private Dictionary<string, object> _Tables;

}
public static class EntityFrameworkMockHelper
{
/// <summary>
/// Returns a mock of a DbContext
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static MockedDbContext<T> GetMockContext<T>() where T : DbContext
{
var instance = new MockedDbContext<T>();
instance.MockTables();
return instance;
}

/// <summary>
/// Use this method to mock a table, which is a DbSet{T} oject, in Entity Framework.
/// Leave the second list null if no adds or deletes are used.
/// </summary>
/// <typeparam name="T">The table data type</typeparam>
/// <param name="table">A List{T} that is being use to replace a database table.</param>
/// <returns></returns>
public static DbSet<T> MockDbSet<T>(List<T> table) where T : class
{
var dbSet = new Mock<DbSet<T>>();
dbSet.As<IQueryable<T>>().Setup(q => q.Provider).Returns(() => table.AsQueryable().Provider);
dbSet.As<IQueryable<T>>().Setup(q => q.Expression).Returns(() => table.AsQueryable().Expression);
dbSet.As<IQueryable<T>>().Setup(q => q.ElementType).Returns(() => table.AsQueryable().ElementType);
dbSet.As<IQueryable<T>>().Setup(q => q.GetEnumerator()).Returns(() => table.AsQueryable().GetEnumerator());
dbSet.Setup(set => set.Add(It.IsAny<T>())).Callback<T>(table.Add);
dbSet.Setup(set => set.AddRange(It.IsAny<IEnumerable<T>>())).Callback<IEnumerable<T>>(table.AddRange);
dbSet.Setup(set => set.Remove(It.IsAny<T>())).Callback<T>(t => table.Remove(t));
dbSet.Setup(set => set.RemoveRange(It.IsAny<IEnumerable<T>>())).Callback<IEnumerable<T>>(ts =>
{
foreach (var t in ts) { table.Remove(t); }
});
dbSet.Setup(set => set.Include(It.IsAny<string>())).Returns(dbSet.Object);
return dbSet.Object;
}

/// <summary>
/// Mocks all the DbSet{T} properties that represent tables in a DbContext.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="mockedContext"></param>
public static void MockTables<T>(this MockedDbContext<T> mockedContext) where T : DbContext
{
Type contextType = typeof(T);
var dbSetProperties = contextType.GetProperties().Where(prop => (prop.PropertyType.IsGenericType) && prop.PropertyType.GetGenericTypeDefinition() == typeof(DbSet<>));
foreach (var prop in dbSetProperties)
{
var dbSetGenericType = prop.PropertyType.GetGenericArguments()[0];
Type listType = typeof(List<>).MakeGenericType(dbSetGenericType);
var listForFakeTable = Activator.CreateInstance(listType);
var parameter = Expression.Parameter(contextType);
var body = Expression.PropertyOrField(parameter, prop.Name);
var lambdaExpression = Expression.Lambda<Func<T, object>>(body, parameter);
var method = typeof(EntityFrameworkMockHelper).GetMethod("MockDbSet").MakeGenericMethod(dbSetGenericType);
mockedContext.Setup(lambdaExpression).Returns(method.Invoke(null, new[] { listForFakeTable }));
mockedContext.Tables.Add(prop.Name, listForFakeTable);
}
}

}

 

参考：

Testing
with a mocking framework (EF6 onwards)

How
to mock an Entity Framework DbContext and its DbSet properties

文件下载地址：http://download.csdn.net/detail/dz45693/9514948