# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Tests for twisted.internet.glibbase.
"""

from __future__ import division, absolute_import

import sys
from twisted.trial.unittest import TestCase
from twisted.internet._glibbase import ensureNotImported



class EnsureNotImportedTests(TestCase):
"""
L{ensureNotImported} protects against unwanted past and future imports.
"""

def test_ensureWhenNotImported(self):
"""
If the specified modules have never been imported, and import
prevention is requested, L{ensureNotImported} makes sure they will not
be imported in the future.
"""
modules = {}
self.patch(sys, "modules", modules)
ensureNotImported(["m1", "m2"], "A message.",
preventImports=["m1", "m2", "m3"])
self.assertEqual(modules, {"m1": None, "m2": None, "m3": None})


def test_ensureWhenNotImportedDontPrevent(self):
"""
If the specified modules have never been imported, and import
prevention is not requested, L{ensureNotImported} has no effect.
"""
modules = {}
self.patch(sys, "modules", modules)
ensureNotImported(["m1", "m2"], "A message.")
self.assertEqual(modules, {})


def test_ensureWhenFailedToImport(self):
"""
If the specified modules have been set to C{None} in C{sys.modules},
L{ensureNotImported} does not complain.
"""
modules = {"m2": None}
self.patch(sys, "modules", modules)
ensureNotImported(["m1", "m2"], "A message.", preventImports=["m1", "m2"])
self.assertEqual(modules, {"m1": None, "m2": None})


def test_ensureFailsWhenImported(self):
"""
If one of the specified modules has been previously imported,
L{ensureNotImported} raises an exception.
"""
module = object()
modules = {"m2": module}
self.patch(sys, "modules", modules)
e = self.assertRaises(ImportError, ensureNotImported,
["m1", "m2"], "A message.",
preventImports=["m1", "m2"])
self.assertEqual(modules, {"m2": module})
self.assertEqual(e.args, ("A message.",))