Mocking the "Properties" property of DirectoryEntry
active-directory, c#, directoryservices, moq, unit-testing
Solution
I don't think that you'll be able to mock or create an instance of `PropertyCollection`. There are ways of overcoming this, but they require you to convert your derived wrapper class to be more of an actual wrapper, encapsulating a `DirectoryEntry` object and providing accessors, not extending it. Once you've done that, you have these options:
- Define the return type of the `Properties` property as one of the underlying collection types that `PropertyCollection` implements (`IDictionary`, `ICollection` or `IEnumerable`), if that is sufficient for your needs
- Create an encapsulating wrapper class with an interface for `PropertyCollection`, and create a new one to wrap `directoryEntry.Properties` each time the `Properties` accessor is called
- Create methods on `IDirectoryEntry`/`DirectoryEntryWrapper` that return what you need without having to expose a `Properties` property
1 might be fine as a workaround, if you're OK accessing the properties through one of the underlying collection types. 2 will require you to implement every method and property of `PropertiesCollection` in the wrapper, calling through to the encapsulated object underneath, but would be the most flexible. The easiest (but least flexible) is 3.
Problem
I'm trying to unit test some Active Directory code, pretty much the same as outlined in this question: Create an instance of DirectoryEntry for use in test The accepted answer suggests implementing a wrapper/adapter for the `DirectoryEntry` class, which I have: ``` public interface IDirectoryEntry : IDisposable { PropertyCollection Properties { get; } } public class DirectoryEntryWrapper : DirectoryEntry, IDirectoryEntry { } ``` The problem is that the "Properties" property on my `IDirectoryEntry` mock is not initialised. Trying to set the mock up like this: ``` this._directoryEntryMock = new Mock<IDirectoryEntry>(); this._directoryEntryMock.Setup(m => m.Properties) .Returns(new PropertyCollection()); ``` Results in the following error: The type 'System.DirectoryServices.PropertyCollection' has no constructors defined As I understand it, this error is thrown when trying to instantiate a class with internal constructors only: The type '...' has no constructors defined I have tried to write a wrapper/adapter for the `PropertyCollection` class but without a public constructor I can't figure out how to instantiate or inherit from the class. So how can I mock/setup the "Properties" property on the `DirectoryEntry` class for testing purposes?