Writing unit tests for IDokanOperations2 implementation: how to make ReadOnlyNativeMemory and DokanFileInfo?

[epa]

Hi, I have a simple filesystem made by implementing the interface IDokanOperations2. I would like to write unit tests for the individual methods. For example to call the CreateFile method with a certain filename, access modes and so on.

To do that I need to create an instance of ReadOnlyNativeMemory<char> to hold the filename. Is there a recommended way to construct tihs given a string or an array of bytes?

I believe I will also need to construct a DokanFileInfo struct, but the documentation states that it cannot be instantiated in C#. Is there a way to get an instance via native code or to mock it somehow?

[LTRData]

I would recommend creating a ReadOnlyNativeMemory<char> using a pinned string. Something like:

const char str = "string";
fixed (char *ptr = str)
{
... = new ReadOnlyNativeMemory<char>(ptr, str.Length);
}

Regarding DokanFileInfo I would say it is a bit more difficult to unit test at this level. I'll think some more about how it could be done. Maybe we could add to the test project some special way of creating a mock-like instance of it with just enough fields filled for tests to work.

[epa]

Thanks. I can see there is a class MockDokanFileInfo which implements an interface IDokanFileInfo, however the methods in IDokanOperations2 are required to take a DokanFileInfo and do not accept this interface. How is the mock class meant to be used?

[LTRData]

Yes, that interface was used in the old implementation where DokanFileInfo was a class and implementation methods accepted that interface so that it could be really mocked. But this is very bad for performance because it needs a heap object created and cleaned up for each I/O request and virtual method lookups each time implementing functions accesses anything in the object.

[epa]

By the way, I think a cast is needed:

            const string str = "string";
            fixed (char *ptr = str)
            {
                ReadOnlyNativeMemory<char> x = new ReadOnlyNativeMemory<char>((nint)ptr, str.Length);
            }

[LTRData]

True. I forgot that!