Helper to create fake filesystem and quick capture its state (or state of a real one).
pip install fsforge==1.0.1
fsforge
- is a toolset defining fake or real filesystem layout.
Gives among others a functionality:
fs
using pyfakefs
.In short it is some kind of syntax' extension to pyfakefs
and
is intended to use with pytest
framework. Allows for absolute
transparency in fs
operations, so that any kind of tests: untit,
functional or end-to-end can be performed in memory - instead of
real hard disc operations (SSD
s can breathe and relax), without any headache nor
enormous setup nor teardown.
The main difference against bare pyfakefs
is that fsforge
uses nice
and clean dict
literals instead of lists of paths. It also allows for reverse
operation - to create the same kind of nested dictionary structure defining
given fs
with just single function call.
Such a result is immediately ready to make assertions on it.
Works with python 2.7
, 3.4
, 3.5
, 3.6
, 3.7
, pypy
and pypy3
.
Created with pyfakefs==3.4.3
.
fs
snapshot.Let's use following structure originated in /tmp/ex
for all further examples:
bash>$ tree /tmp/ex
/tmp/ex
├── dir_a
│ ├── sub_empty_dir
│ ├── sub_dir_with_a_file
│ │ ├── app_dump.json
│ │ └── file_1.txt
│ └── file_2.txt
├── dir_b
│ ├── special_file.txt
│ └── file_4.bin
├── empty_dir
└── special_file_2.txt
We can collect a snapshot of this layout with:
import pprint
from fsforge import take_fs_snapshot
tree = take_fs_snapshot('/tmp/ex')
pprint.pprint(tree)
will output such a tree
:
{
'dir_a': {
'sub_empty_dir': {},
'sub_dir_with_a_file': {
'app_dump.json': None,
'file_1.txt': None
},
'file_2.txt': None,
},
'dir_b': {
'app_dump.json': None,
'special_file.txt': None,
'file_4.bin': None
},
'empty_dir': {},
'special_file_2.txt`: None
}
The resulting tree
is a pure dict
. fsforge
uses magic
relation and similarity of directory to a python's dictionary.
Directories are recognized by being dict
instances.
Any other value type in the tree
is treat as a file.
fsforge
distinguishes only dict
(as directories)
and non dict
(files) while traversing the tree.
Now fsforge
can use such kind of tree
to perform needed pyfakefs
'
calls to recreate the structure in memory for some pytest
tests:
import os
from fsforge import create_fs
def test_that(fs):
create_fs(fs, tree, "/tmp/ex"):
# everything is now set up:
assert os.path.isdir("/tmp/ex/dir_a/sub_dir_with_a_file")
assert os.path.isfile("/tmp/ex/dir_a/file_2.txt")
In the code above:
fs
is a fixture automatically accessible in tests as soon as
you have pyfakefs
package installed. It can also be a
FakeFilesystem
object instance imported from pyfakefs
.fs
could also be a fsforge.RealFS
object. Real writes will be performed.tree
is reused dictionary from previous code snippets"/tmp/ex"
is a origin of "mount point" of given structure,
pyfakefs
will anchor items specified in tree
to this path.The application you test may make some changes to given file system.
After some time you can collect a snapshot of the fs
structure and
make needed assertions on the changes made to its state.
E.g. probably some files were removed or created, some content appended. Whatever.. Of course you may not be interested with all of that, that's why there is:
The take_fs_snapshot
function takes a file system mask definition as an argument.
File processor is just a function provided by you taking given file path and returning
anything you need from that file, e.g. it's contents (or any processing result or None
).
def reader(file_path):
with open(file_path, 'r') as file_:
return file_.read()
def json_reader(file_path):
content = json.loads(reader(file_path))
return json.dumps(content["some section only"])
Assume we have a file system from /tmp/ex
from beginning of this readme.
And we want to read:
dir_b
whose name contains file
substringapp_dump.json
- in whatever directory but "some section only" is
interestingSo let's create a mask and call it:
from fsforge import iddle_file_processor
# iddle_file_processor returns None regardless of call argument, is used to note
# files existence (without that file is ignored and does not appear in the result tree)
mask = {
'dir_b': {
# any file containing 'file' substring
'*file*': reader,
},
'**': {
# any file named app_dump.json in whatever path
'app_dump.json': json_reader,
},
# Note any file in top level directory (but don't read it)
'*': iddle_file_processor,
}
result = take_fs_snapshot("/tmp/ex", mask)
from pprint import pprint
pprint(result)
{
'dir_a': {
'sub_empty_dir': {},
'sub_dir_with_a_file': {
'app_dump.json': '{"some section only": "its contents"}',
},
},
'dir_b': {
'app_dump.json': '{"some section only": "its contents in dir_b"},
'special_file.txt': "distinguished content",
'file_4.bin': "contents of file_4"
},
'empty_dir': {},
'special_file_2.txt': None,
}
Does that result look similar? Yes, it's the same kind of tree, but files have strings instead of nones.
It can be used to recreate the fs
with these strings as contents of the new files.