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我一直在为只能获取和返回字符串的 COM 对象开发一个包装器。COM 对象的接口如下所示：

    interface IMapinfo
    {
        void Do(string cmd);
        string Eval(string cmd);
    }

现在我已经制作了包含如下基本功能的类：

    public class Table 
    {
        IMapinfo MI;
        public string Name
        {
            //pass the command to the COM object and get back the name.
            get{return MI.Eval("TableInfo(1,1")");}
        }

    }

现在我想对这些类进行单元测试，而不必每次都创建真正的 COM 对象，设置世界然后运行测试。所以我一直在研究使用模拟对象，但我对在这种情况下如何使用模拟有点困惑。

我打算使用起订量，所以我这样写了这个测试：

        [Test]
        public void MockMapinfo()
        {
            Moq.Mock<Table> MockTable = new Moq.Mock<Table>();
            MockTable.ExpectGet(n => n.Name)
                .Returns("Water_Mains");

            Table table = MockTable.Object;
            var tablename = table.Name;

            Assert.AreEqual("Water_Mains", tablename,string.Format("tablename is {0}",tablename));
            Table d = new Table();
         }

这是模拟我的 COM 对象的正确方法吗？发送到 eval 函数的字符串如何正确？还是我做错了？

4

1 回答 1

3

这是重复的吗？我将如何使用 COM OLE 对象进行 TDD

EDIT: Looks like you're asking the same question, but to validate your mocking code (OOPS).

You're not quite there for your mocking scenario. You're in the right that you want to isolate external dependencies, and your COM object certainly meets that criteria. Though I'm not a moq guy (I prefer RhinoMocks) the idea behind mocks is interaction testing...

Interaction testing is about how cohesive sets of objects work together. A valid test in this scenario would be to write a test for the component that is dependent on your COM object's behavior.

In this case, your "Table" which acts like a wrapper for your COM object, is also dependent on the COM object's behavior. For argument sake, let's say your Table object performs custom logic against the values that are returned from your COM object.

Now you can write isolated tests for your Table object while simulating your COM object's behavior using Mocks.

public class Table
{
   public Table(IMapInfo map)
   {
      _map = map;
   }

   public string Name
   {
      get 
      {
        string value = _map.Eval("myexpression");
        if (String.IsNullOrEmpty(value))
        {
            value = "none";
        }
        return value;
      }
   }

   private IMapInfo _map;
}

[TestFixture]
public class TableFixture // is this a pun?
{
   [Test]
   public void CanHandleNullsFromCOM()
   {
       MockRepository mocks = new MockRepository(); // rhino mocks, btw
       IMapInfo map = mocks.CreateMock<IMapInfo>();

       using (mocks.Record())
       {
          Expect.Call(map.Eval("myexpression").Return(null);
       }

       using (mocks.PlayBack())
       {
          Table table = new Table(map);
          Assert.AreEqual("none", table.Name, "We didn't handle nulls correctly.");
       }

       mocks.verify();
   }
}

Maybe your COM object throws exceptions when it's called, or maybe it doesn't handle string expressions very well. We're actually testing how our Table object interacts with the IMapInfo without being tied to the COM object's implementation. We're also enforcing a relationship between Table and IMapInfo in that the IMapInfo object must be called during the test.

Hope this helps.

于 2008-11-20T06:18:28.510 回答