# pyproxyfs - a lightweight filesystem proxy object

The aim of pyproxyfs is to provide a filesystem class that you can use
for doing much of your file handling... but that can easi;ly be mocked
for specific testing purposes.

If, instead of using open, os.rename and os.listdir you use the
pyproxyfs equivalents you can expect to be able to make a simple
filesystem using the builtin TestFS class and write tests around that.

For example:

def show_conf_files(dirtolist, filesystem=None):
    from pyproxyfs import Filesystem
    if not filesystem:
       filesystem = Filesystem()
    files = filesystem.listdir(dirtolist)
    import re
    cfgpat = re.compile(".*\\.cfg$")
    cfg_files = [fn for fn in files if cfgpat.match(fn)]
    return cfg_files


this might be your application code.

You could then test it relatively simply:

def test_show_conf_files():
    """
    >>> test_show_conf_files()
    ['a.cfg', 'b.cfg']
    """
    from pyproxyfs import TestFS
    fs = TestFS({
        "somedir/a.cfg": "",
        "somedir/a.txt": "",
        "somedir/b.cfg": "",
        "somedir/run.py": ""
        })
    return show_conf_files("somedir", filesystem=fs)


## Limitations

The pyproxyfs is not designed to be a full filesystem proxy, it's just
a simple and quick way to test.

There is no way to write to the TestFS system yet; native filesystem
writes work through the proxy tho as it just uses `open` directly.
