如何使用NSubstitute模拟DbContext，然后添加/删除数据

Question

我需要模拟EF的DbContext 。 我在这里使用该方法，并且效果很好。

// mock a DbSet
var mockDbSet = Substitute.For<DbSet<Foo>, IQueryable<Foo>>();
var data = new List<Foo>().AsQueryable();
((IQueryable<Foo>)mockDbSet).Provider.Returns(data.Provider);
((IQueryable<Foo>)mockDbSet).Expression.Returns(data.Expression);
((IQueryable<Foo>)mockDbSet).ElementType.Returns(data.ElementType);
((IQueryable<Foo>)mockDbSet).GetEnumerator().Returns(data.GetEnumerator());
// now add it to a mock DbContext
var mockContext = Substitute.For<MyDbContextClass>();
mockContext.Set<Foo>().Returns(mockDbSet);

但是在某些测试中，我需要能够调用mockContext.Set<Foo>().Add(someFoo)和mockContext.Set<Foo>().Remove(otherFoo) ，并使基础的添加/删除逻辑起作用。

我尝试了这个：

mockDbSet.When(x => x.Add(Arg.Any<Foo>())).Do(x => data.Add(x.Arg<Foo>()));

但是它与Collection was modified; enumeration operation may not execute.抛出时Collection was modified; enumeration operation may not execute. Collection was modified; enumeration operation may not execute.

那么如何实现添加/删除功能？

Answer 1

您不想将其添加到集合中。 您想要做的就是检查它（添加/删除/等）是否被调用，以及调用它的可能。

// arrange - check what it was called with. You place asserts in the body of the `Do` expression. Place this before your call that actually executes the code
mockDbSet.Add(Arg.Do<Foo>(foo =>
{
    Assert.IsNotNull(foo);
    // Assert other properties of foo
}));

// act


// assert. Make sure that it was actually called
mockDbSet.Received(1).Add(Arg.Any<Foo>());

---

如果要在以后的测试中添加Foo ，则可以保留对Foo List的引用。

// mock a DbSet
var mockDbSet = Substitute.For<DbSet<Foo>, IQueryable<Foo>>();
var fooList = new List<Foo>();
var data = fooList.AsQueryable();
// rest of your code unchanged

// add it from the code being tested through the mock dbset
mockDbSet.Add(Arg.Do<Foo>(foo =>
{
    fooList.Add(foo);
    // at this point you have to recreate the added IQueryable
    data = fooList.AsQueryable();
    // rest of code you had to add this to the mockDbSet
}));


// act

Answer 2

@Stilgar的评论使我了解了EntityFramework.Testing库，它解决了这个问题 。

所以我用这个库替换了我的东西（不用担心的另一件事）。