Jmock Mockery, mocking a file system object

Question

I want to be able to mock the File object in java using Mockery. I seems like we may not be able to create an interface for the File in java. Is this possible?

EDIT:

I need to test the indexDoc function in Indexer Class.

@Test
public void testindexDocs()
{       
  final File f = mockFile.mock(File.class);
  File file = new File("test");     
  mockFile.setImposteriser(ClassImposteriser.INSTANCE);     
  final String[] files = {
      "C:\\test\\",
      "C:\\test\\test1.html",
      "C:\\test\\test2",
      "C:\\test\\test3.html"};          
  mockFile.checking(new Expectations(){
    {
      one(f).list();will(returnValue(files)); 
    }
  });       
  //TODO test if list() how many time i have called
  //Document doc = HTMLDocument.Document(file); in function indexDocs  
}

Index Docs function in Indexer class

private static void indexDocs(File file) throws Exception{
  //Check for file to be a directory or file to be indexed look for html files and add to document      
  if(file.isDirectory()){
    String[] files = file.list();
    Arrays.sort(files);
    for (int i = 0; i < files.length; i++)    // recursively index them
      indexDocs(new File(file, files[i]));
  } else if(file.getPath().endsWith(".html") || file.getPath().endsWith("htm")){
    // Get the document from HTMLDocument class which takes care of stripping of HTML tag, get the path
    // of HTML file and title of HTML document.
    Document doc = HTMLDocument.Document(file);

    // TODO Get the book of HTML, it can be a part of HTML document class.   
    writer.addDocument(doc);
  }
}

Answer 1

Don't mock the file system. We tried to do this in the early days and it diverted us from using tests to guide the design.

From a quick look at your code, there are two things going on, one is file navigation, the other is html stripping. Perhaps one option would be to introduce a html stripping object (passed in as a collaborator) and mock that, then write tests against examples in a real file system.

Answer 2

Jmock can mock concrete classes. Just do

Mockery context = new Mockery();

context.setImposteriser(ClassImposteriser.INSTANCE);

Answer 3

The problems your having are the exact reason, one should use abstractions rather than concrete classes.