import sys
import io
import unittest
import gc
import contextlib


TESTFN = '@test'

def run_unittest(*classes):
    suite = unittest.TestSuite()
    for c in classes:
        suite.addTest(c)
    runner = unittest.TestRunner()
    result = runner.run(suite)
    msg = "Ran %d tests" % result.testsRun
    if result.skippedNum > 0:
        msg += " (%d skipped)" % result.skippedNum
    print(msg)

def can_symlink():
    return False

def skip_unless_symlink(test):
    """Skip decorator for tests that require functional symlink"""
    ok = can_symlink()
    msg = "Requires functional symlink implementation"
    return test if ok else unittest.skip(msg)(test)

def create_empty_file(name):
    open(name, "w").close()

@contextlib.contextmanager
def disable_gc():
    have_gc = gc.isenabled()
    gc.disable()
    try:
        yield
    finally:
        if have_gc:
            gc.enable()

def gc_collect():
    gc.collect()
    gc.collect()
    gc.collect()

@contextlib.contextmanager
def captured_output(stream_name):
    org = getattr(sys, stream_name)
    buf = io.StringIO()
    setattr(sys, stream_name, buf)
    try:
        yield buf
    finally:
        setattr(sys, stream_name, org)

def captured_stderr():
    return captured_output("stderr")