Mocking IO operations in Nunit using Typemock

Question

I have the following method.

public string CreateFile(string path, string fileName)
{
    string fullPath = path + "ExportedFiles\\";
    if (Directory.Exists(fullPath))
    {
        DirectoryInfo dir = new DirectoryInfo(fullPath);
        foreach (FileInfo fi in dir.GetFiles())
        {
            fi.Delete();
        }
    }
    else
    {
        Directory.CreateDirectory(fullPath);
    }
    string filePath = fullPath + fileName;
    return filePath;
}

I attempted to used the following in my test case.

[Test, Isolated] 
public void TestCreateFileIfPathExists() 
{ 
    Isolate.WhenCalled(() => System.IO.Directory.Exists("gsgs")).WillReturn(true);
    Isolate.WhenCalled(() => testMyClass.CreateFile(@"D:\testFolder\","TestFile")).CallOriginal(); 
    string result = testMyClass.CreateFile(@"D:\testFolder\", "TestFile");
    Assert.AreEqual("D:\\testFolder\\ExportedFiles\\TestFile", result);
} 

It's throwing the following typemock exception.

TypeMock.TypeMockException : * No method calls found in recording block. Please check: * Are you trying to fake a field instead of a property? * Are you are trying to fake an unsupported mscorlib type?

Is there any way to solve this?

Answer 1

If you look at the last question of the exception that you are getting,

* Are you are trying to fake an unsupported mscorlib type?

there is actually a web address after that in the exception, which reads

See supported types here: http://www.typemock.com/mscorlib-types

When you go there, you will notice:

Notably absent from this list is the System.IO.Directory class, which appears to not be supported TypeMock as of this writing. This is the line that is causing your error.