Test Daemon For Python using Nose

Last week we had a great night with Tim Ottinger, playing with Python to analyze commit history.

One thing impressed me is Tim's Python develop environment. His tests are running automatically after a change. I didn't caught up how he made it work, and cannot find a apropiate key word to google. So here is my own version.

The idea is quite simple: Use nose API to re-run tests every time a source change is detected. 

while True:
    while not sourceChanged(dirs):
        time.sleep(1)
    nose.run()

Only thing needs special attention is to isolate test modules by provide option `–with-isolation`, so nose will reload them before each `nose.run`. For file change detection, library watchdog is used. 1

Two improvements I can think of are:

  1. Not only monitor *.py files, but all files. Configuration files can also have an impact on test result.
  2. Ignore version control files, because these folders are always filled by tones of files.

The complete source code is shown below: 

import sys
import time
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
import nose
import os
from itertools import takewhile


def cls():
    os.system('cls' if os.name=='nt' else 'clear')


class TestMonitor(FileSystemEventHandler):

    def __init__(self):
        FileSystemEventHandler.__init__(self)
        self.modified = False

    def on_any_event(self, event):
        print(event.src_path)
        self.modified = True

    @property
    def path(self):
        where = list(takewhile(lambda a: not a.startswith("-"), sys.argv[1:]))
        for i, v in enumerate(sys.argv):
            if v == "-w" or v == "--where":
                where.append(sys.argv[i+1])
        where = filter(os.path.isdir, where)
        if len(where) == 0:
            return ["."]
        return where

    def testIt(self):
        cls()
        nose.run()
        self.modified = False

    def run(self):
        sys.argv.append("--with-isolation")

        observer = Observer()
        for p in self.path:
            observer.schedule(self, p, recursive = True)
        observer.start()

        self.testIt()

        try:
            while True:
                time.sleep(1)
                if self.modified:
                    self.testIt()
        except KeyboardInterrupt:
            observer.stop()
        observer.join()


if __name__ == "__main__":
    TestMonitor().run()

Footnotes:

1

https://github.com/gorakhargosh/watchdog

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