如何在单元测试中使用Moq和DbFunctions来防止NotSupportedException? [英] How do I use Moq and DbFunctions in unit tests to prevent a NotSupportedException?

问题描述

我目前正在尝试对通过实体框架运行的查询运行某些单元测试.查询本身在实时版本上运行没有任何问题，但是单元测试始终失败.

I'm currently attempting to run some unit tests on a query that is running through the Entity Framework. The query itself runs without any issues on the live version, but the unit tests are always failing.

我已经将其范围缩小到了DbFunctions.TruncateTime的用法，但是我不知道有什么方法可以使单元测试反映出实时服务器上发生的事情.

I've narrowed this down to my usage of DbFunctions.TruncateTime, but I don't know of a way around this to get the unit tests to reflect what is happening on the live server.

这是我使用的方法:

    public System.Data.DataTable GetLinkedUsers(int parentUserId)
    {
        var today = DateTime.Now.Date;

        var query = from up in DB.par_UserPlacement
                    where up.MentorId == mentorUserId
                        && DbFunctions.TruncateTime(today) >= DbFunctions.TruncateTime(up.StartDate)
                        && DbFunctions.TruncateTime(today) <= DbFunctions.TruncateTime(up.EndDate)
                    select new
                    {
                        up.UserPlacementId,
                        up.Users.UserId,
                        up.Users.FirstName,
                        up.Users.LastName,
                        up.Placements.PlacementId,
                        up.Placements.PlacementName,
                        up.StartDate,
                        up.EndDate,
                    };

        query = query.OrderBy(up => up.EndDate);

        return this.RunQueryToDataTable(query);
    }

如果我注释掉带有DbFunctions的行，则测试全部通过(那些正在检查仅运行给定日期的有效结果的测试除外).

If I comment out the lines with DbFunctions in, the tests all pass (except for the ones that are checking that only valid results for a given date are run).

是否可以提供模拟版本的DbFunctions.TruncateTime以在这些测试中使用?本质上，它应该只返回Datetime.Date，但这在EF查询中不可用.

Is there a way I can provide a mocked version of DbFunctions.TruncateTime to use in these tests? Essentially it should just be returning Datetime.Date, but that isn't available in EF queries.

这是使用日期检查的失败测试:

Here's the test that's failing that uses the date check:

    [TestMethod]
    public void CanOnlyGetCurrentLinkedUsers()
    {
        var up = new List<par_UserPlacement>
        {
            this.UserPlacementFactory(1, 2, 1), // Create a user placement that is current
            this.UserPlacementFactory(1, 3, 2, false) // Create a user placement that is not current
        }.AsQueryable();

        var set = DLTestHelper.GetMockSet<par_UserPlacement>(up);

        var context = DLTestHelper.Context;
        context.Setup(c => c.par_UserPlacement).Returns(set.Object);

        var getter = DLTestHelper.New<LinqUserGetLinkedUsersForParentUser>(context.Object);

        var output = getter.GetLinkedUsers(1);

        var users = new List<User>();
        output.ProcessDataTable((DataRow row) => students.Add(new UserStudent(row)));

        Assert.AreEqual(1, users.Count);
        Assert.AreEqual(2, users[0].UserId);
    }

:这是来自相关测试的消息和调试跟踪:

Edit 2: This is the message and debug trace from the test in question:

Test Result: Failed

Message: Assert.AreEqual failed. Expected:<1>. Actual:<0>

Debug Trace: This function can only be invoked from LINQ to Entities

根据我的阅读，这是因为尽管有实时版本(因为它正在查询SQL)，但是在此位置没有可用于单元测试的此方法的LINQ to Entities实现.服务器).

From what I've read, this is because there isn't a LINQ to Entities implementation of this method that could be used in this place for the Unit Test, although there is on the live version (as it's querying an SQL server).

推荐答案

感谢大家的所有帮助，在阅读了qujck提到的垫片后，我设法找到了对我有用的解决方案.添加了伪造的EntityFramework程序集后，我可以通过将其更改为以下内容来修复这些测试:

Thanks for all of the help everyone, I managed to track down a solution that worked for me after reading up on shims that qujck mentioned. After adding a fake assembly of EntityFramework, I was able to fix these tests by changing them to the following:

[TestMethod]
public void CanOnlyGetCurrentLinkedUsers()
{
    using (ShimsContext.Create())
    {
        System.Data.Entity.Fakes.ShimDbFunctions.TruncateTimeNullableOfDateTime =
            (DateTime? input) =>
            {
                return input.HasValue ? (DateTime?)input.Value.Date : null;
            };

        var up = new List<par_UserPlacement>
        {
            this.UserPlacementFactory(1, 2, 1), // Create a user placement that is current
            this.UserPlacementFactory(1, 3, 2, false) // Create a user placement that is not current
        }.AsQueryable();

        var set = DLTestHelper.GetMockSet<par_UserPlacement>(up);

        var context = DLTestHelper.Context;
        context.Setup(c => c.par_UserPlacement).Returns(set.Object);

        var getter = DLTestHelper.New<LinqUserGetLinkedUsersForParentUser>(context.Object);

        var output = getter.GetLinkedUsers(1);
    }

    var users = new List<User>();
    output.ProcessDataTable((DataRow row) => users.Add(new User(row)));

    Assert.AreEqual(1, users.Count);
    Assert.AreEqual(2, users[0].UserId);
}

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