Unit Testing File I/O

Question

Reading through the existing unit testing related threads here on Stack Overflow, I couldn\'t find one with a clear answer about how to unit test file I/O operations. I have

Answer 1

Check out Tutorial to TDD using Rhino Mocks and SystemWrapper.

SystemWrapper wraps many of System.IO classes including File, FileInfo, Directory, DirectoryInfo, ... . You can see the complete list.

In this tutorial I'm showing how to do testing with MbUnit but it's exactly the same for NUnit.

Your test is going to look something like this:

[Test]
public void When_try_to_create_directory_that_already_exists_return_false()
{
    var directoryInfoStub = MockRepository.GenerateStub();
    directoryInfoStub.Stub(x => x.Exists).Return(true);
    Assert.AreEqual(false, new DirectoryInfoSample().TryToCreateDirectory(directoryInfoStub));

    directoryInfoStub.AssertWasNotCalled(x => x.Create());
}