如何使用 Moq 模拟集合

Question

我对单元测试和模拟是全新的，并且仍然在耳后湿漉漉。我正在使用 Moq 框架，我需要模拟一个集合，以便它产生一个具有我提供的值的成员。

有问题的集合类是System.Configuration.SettingsPropertyCollection，其中包含SettingsProperty 对象。

反过来，SettingsProperty 有一个 Attributes 属性，该属性返回一个 SettingsAttributeDictionary。

我需要我的集合生成一个SettingsProperty，它在其Attributes.SettingsAttributeDictionary 中有一个自定义属性（派生自System.Attribute）。

我真的很难解决这个问题，但到目前为止无济于事。我试过伸出我的舌头并用它做鬼脸，但没有任何效果。

这是我到目前为止尝试过的代码，在代码中注释的地方抛出了一个异常，所以当然测试总是失败。

    [TestMethod]
    public void GetPropertySettings_Should_Return_Default_Values_When_Device_Not_Registered()
        {
        const string deviceName = "My.UnitTest";
        const string deviceType = "Switch";
        var deviceId = String.Format("{0}.{1}", deviceName, deviceType);
        Mock<IProfile> mockProfile = new Mock<IProfile>();
        Mock<SettingsContext> mockSettingsContext = new Mock<SettingsContext>();
        // Construct a SettingsPropertyCollection populated with a single property.
        // The single property will have a fixed name and default value, and will also have a single
        // attribute, giving teh ASCOM DeviceId.
        var deviceAttribute = new ASCOM.DeviceIdAttribute(deviceId);
        var attributes = new SettingsAttributeDictionary();
        attributes.Add(typeof(DeviceIdAttribute), deviceAttribute);
        var settingsProperty = new SettingsProperty(SettingName, typeof(string), null, false, SettingDefaultValue, SettingsSerializeAs.String, attributes, true, true);
        var propertyCollection = new SettingsPropertyCollection();
        propertyCollection.Add(settingsProperty);

        // Now comes the interesting part where we call our IProfile - this is where we really need Moq.
        // Expectations:
        //  - mockProfile must have it's DeviceType set.
        //  - mockProfile's device type (captured in setDeviceType) must match deviceType.
        //  - The returned SettingsPropertyValueCollection must not be empty.
        //  - The returned SettingsPropertyValueCollection must have exactly one entry.
        //  - The entry must match the value of SettingDefaultValue. 

        // Expectation: IProfile must have its DeviceType set.  We capture the value into setDeviceType.
        var setDeviceType = String.Empty;
        mockProfile.SetupSet(x => x.DeviceType).Callback(y => setDeviceType = y);

        // Finally, it is time to call the method we want to test
        var settingsProvider = new SettingsProvider(mockProfile.Object);

        // THE NEXT LINE THROWS AN EXCEPTION
        // IF I TRY TO STEP INTO IT, IT NEVER RETURNS AND THE TEST RUN JUST ENDS.
        var result = settingsProvider.GetPropertyValues(mockSettingsContext.Object, propertyCollection);

        // Now lets verify that everything went as expected
        // First, let's test that the parsing of DeviceId was as expected: IProvider.DeviceType was set to the expected value
        Assert.AreEqual(deviceType, setDeviceType);
        // Then let's test that the methods of IProvider that we mocked were called
        mockProfile.VerifyAll();

        // With this done, let's turn to the output of the method
        // Firstly, we test that the resulting collection contains exactly one item of the type SettingsPropertyValue
        Assert.IsTrue(result.Count > 0);
        Assert.AreEqual(1, result.Count);
        Assert.IsTrue(result.OfType<SettingsPropertyValue>().Count() > 0);

        // Then let's inspect the contained SettingsProviderValue further
        var settingsPropertyValue = result.OfType<SettingsPropertyValue>().First();

        // First IsDirty flag must never be set
        Assert.IsFalse(settingsPropertyValue.IsDirty);

        // The PropertyValue must be the default value we passed in
        Assert.AreEqual(SettingDefaultValue, settingsPropertyValue.PropertyValue);
        }

抛出的异常（由测试运行程序报告）是：

测试方法 ASCOM.Platform.Test.SettingsProviderTest.GetPropertySettings_Should_Return_Default_Values_When_Device_Not_Registered 抛出异常：System.ArgumentException：System.Configuration.SettingsContext 类型实现 ISerializable，但未能提供反序列化构造函数。

Answer 1

我相信您需要设置您的模拟 SettingsProperty 的 Attributes 属性以返回您的模拟 SettingsAttributeDictionary 和 然后 设置您的模拟 SettingsAttributeDictionary 的索引器以返回您想要的值，例如

mockItem.SetupGet(x => x.Attributes).Returns(mockAttributes);

mockAttributes.SetupGet(x => x[It.IsAny<System.Type>()])
              .Returns(deviceAttribute);

编辑

Moq 使用的 Castle DynamicProxy 类中引发了异常。我相信这与 Moq 如何模拟可序列化的对象有关。如果 Castle 无法在签名为 (SerializationInfo, StreamingContext) 的可序列化对象上找到非公共构造函数，则抛出此异常。您可以做的是更改自定义 SettingsProvider 的 GetPropertyValues 方法，使其接受 Hashtable 而不是 SettingsContext，并为方法调用提供模拟 Hashtable 而不是模拟 SettingsContext。 Hashtable 具有所需的构造函数，因此也许这会起作用。坚持使用 SettingsContext 类型的参数而不是 Hashtable 并没有真正的优势，因为 SettingsContext 只是微不足道地从 Hashtable 派生，即它不添加任何成员。