IPython/utils/tests/test_io.py

# encoding: utf-8
"""Tests for io.py"""

# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.


import sys
from io import StringIO

from subprocess import Popen, PIPE
import unittest

from IPython.utils.io import IOStream, Tee, capture_output


def test_tee_simple():
    "Very simple check with stdout only"
    chan = StringIO()
    text = 'Hello'
    tee = Tee(chan, channel='stdout')
    print(text, file=chan)
    assert chan.getvalue() == text + "\n"


class TeeTestCase(unittest.TestCase):

    def tchan(self, channel):
        trap = StringIO()
        chan = StringIO()
        text = 'Hello'
        
        std_ori = getattr(sys, channel)
        setattr(sys, channel, trap)

        tee = Tee(chan, channel=channel)

        print(text, end='', file=chan)
        trap_val = trap.getvalue()
        self.assertEqual(chan.getvalue(), text)

        tee.close()

        setattr(sys, channel, std_ori)
        assert getattr(sys, channel) == std_ori

    def test(self):
        for chan in ['stdout', 'stderr']:
            self.tchan(chan)

def test_io_init():
    """Test that io.stdin/out/err exist at startup"""
    for name in ('stdin', 'stdout', 'stderr'):
        cmd = "from IPython.utils import io;print(io.%s.__class__)"%name
        with Popen([sys.executable, '-c', cmd], stdout=PIPE) as p:
            p.wait()
            classname = p.stdout.read().strip().decode('ascii')
        # __class__ is a reference to the class object in Python 3, so we can't
        # just test for string equality.
        assert 'IPython.utils.io.IOStream' in classname, classname

class TestIOStream(unittest.TestCase):

    def test_IOStream_init(self):
        """IOStream initializes from a file-like object missing attributes. """
        # Cause a failure from getattr and dir(). (Issue #6386)
        class BadStringIO(StringIO):
            def __dir__(self):
                attrs = super().__dir__()
                attrs.append('name')
                return attrs
        with self.assertWarns(DeprecationWarning):
            iostream = IOStream(BadStringIO())
            iostream.write('hi, bad iostream\n')

        assert not hasattr(iostream, 'name')
        iostream.close()

    def test_capture_output(self):
        """capture_output() context works"""
        
        with capture_output() as io:
            print("hi, stdout")
            print("hi, stderr", file=sys.stderr)

        self.assertEqual(io.stdout, "hi, stdout\n")
        self.assertEqual(io.stderr, "hi, stderr\n")