trees and test suites -- a proposal

Well, since Python is so much fun, I decided to take a look at what I
could do in the test suite. And there I noticed the todo item to
check the entries file against the desired results. So I decided to
work on that.

Then, I thought that really, the expected results and the hierarchy of
entries files were both really trees, and I could just convert them
all to trees and then compare them.

Then I realized that many of the things we want to compare are really
representations of trees in the filesystem (the disk filesystem, not
the SVN filesytem). So I figured, why not create a generic tree
structure, and have lots of mappings to it?

So that's what I did.

So, with the history out of the way, here's the details. As I see it,
there are a large number of different representations of what the
on-disk filesystem looks like (not even counting the one in the SVN
filesystem, which the black box testing doesn't see).

 - The output of svn commands like checkout.
 - The SVN/entries files
 - the CVS/Entries files, for cvs2svn
 - The actual on-disk files
 - The expected results (which may or may not be the same as one of
 the above)

There may be more as well.

So, we should have a generic representation of all of these, and a way
to transform to that representation.

The way I have constructed that representation is with a single python
class, SVNTreeNode. However, you shouldn't ever have to deal with
that class at all. The interfaces will look like so:

  # create a tree from the expected paths
  exp_tree = create_tree_from_paths(greek_paths)

  # create a tree from the output
  result_tree = create_tree_from_output(output)

  # make sure they're the same
  if not(compare_trees(exp_tree, result_tree)):
    print "Eeek!"

I've already written create_tree_from_paths(), and it parses the
greek_trees variable in xml_tests.py properly. I've also written the
comparison function, and the rest of the basic infrastructure. Before
I wrote parsers for the rest, I'd like to make sure that no one has
serious problems with the way I'm going about this.

Attached is svn_tree.py, with the current implementation.
           
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