summaryrefslogtreecommitdiffstats
path: root/Lib/test/test_warnings.py
blob: 953b2827be2dd02b9963e0748f66967ae43a11cd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
from contextlib import contextmanager
import linecache
import os
from io import StringIO
import sys
import unittest
import subprocess
from test import support
from test.script_helper import assert_python_ok

from test import warning_tests

import warnings as original_warnings

py_warnings = support.import_fresh_module('warnings', blocked=['_warnings'])
c_warnings = support.import_fresh_module('warnings', fresh=['_warnings'])

@contextmanager
def warnings_state(module):
    """Use a specific warnings implementation in warning_tests."""
    global __warningregistry__
    for to_clear in (sys, warning_tests):
        try:
            to_clear.__warningregistry__.clear()
        except AttributeError:
            pass
    try:
        __warningregistry__.clear()
    except NameError:
        pass
    original_warnings = warning_tests.warnings
    original_filters = module.filters
    try:
        module.filters = original_filters[:]
        module.simplefilter("once")
        warning_tests.warnings = module
        yield
    finally:
        warning_tests.warnings = original_warnings
        module.filters = original_filters


class BaseTest(unittest.TestCase):

    """Basic bookkeeping required for testing."""

    def setUp(self):
        # The __warningregistry__ needs to be in a pristine state for tests
        # to work properly.
        if '__warningregistry__' in globals():
            del globals()['__warningregistry__']
        if hasattr(warning_tests, '__warningregistry__'):
            del warning_tests.__warningregistry__
        if hasattr(sys, '__warningregistry__'):
            del sys.__warningregistry__
        # The 'warnings' module must be explicitly set so that the proper
        # interaction between _warnings and 'warnings' can be controlled.
        sys.modules['warnings'] = self.module
        super(BaseTest, self).setUp()

    def tearDown(self):
        sys.modules['warnings'] = original_warnings
        super(BaseTest, self).tearDown()


class FilterTests(object):

    """Testing the filtering functionality."""

    def test_error(self):
        with original_warnings.catch_warnings(module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("error", category=UserWarning)
            self.assertRaises(UserWarning, self.module.warn,
                                "FilterTests.test_error")

    def test_ignore(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("ignore", category=UserWarning)
            self.module.warn("FilterTests.test_ignore", UserWarning)
            self.assertEqual(len(w), 0)

    def test_always(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("always", category=UserWarning)
            message = "FilterTests.test_always"
            self.module.warn(message, UserWarning)
            self.assertTrue(message, w[-1].message)
            self.module.warn(message, UserWarning)
            self.assertTrue(w[-1].message, message)

    def test_default(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("default", category=UserWarning)
            message = UserWarning("FilterTests.test_default")
            for x in range(2):
                self.module.warn(message, UserWarning)
                if x == 0:
                    self.assertEqual(w[-1].message, message)
                    del w[:]
                elif x == 1:
                    self.assertEqual(len(w), 0)
                else:
                    raise ValueError("loop variant unhandled")

    def test_module(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("module", category=UserWarning)
            message = UserWarning("FilterTests.test_module")
            self.module.warn(message, UserWarning)
            self.assertEqual(w[-1].message, message)
            del w[:]
            self.module.warn(message, UserWarning)
            self.assertEqual(len(w), 0)

    def test_once(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("once", category=UserWarning)
            message = UserWarning("FilterTests.test_once")
            self.module.warn_explicit(message, UserWarning, "test_warnings.py",
                                    42)
            self.assertEqual(w[-1].message, message)
            del w[:]
            self.module.warn_explicit(message, UserWarning, "test_warnings.py",
                                    13)
            self.assertEqual(len(w), 0)
            self.module.warn_explicit(message, UserWarning, "test_warnings2.py",
                                    42)
            self.assertEqual(len(w), 0)

    def test_inheritance(self):
        with original_warnings.catch_warnings(module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("error", category=Warning)
            self.assertRaises(UserWarning, self.module.warn,
                                "FilterTests.test_inheritance", UserWarning)

    def test_ordering(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.resetwarnings()
            self.module.filterwarnings("ignore", category=UserWarning)
            self.module.filterwarnings("error", category=UserWarning,
                                        append=True)
            del w[:]
            try:
                self.module.warn("FilterTests.test_ordering", UserWarning)
            except UserWarning:
                self.fail("order handling for actions failed")
            self.assertEqual(len(w), 0)

    def test_filterwarnings(self):
        # Test filterwarnings().
        # Implicitly also tests resetwarnings().
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.filterwarnings("error", "", Warning, "", 0)
            self.assertRaises(UserWarning, self.module.warn, 'convert to error')

            self.module.resetwarnings()
            text = 'handle normally'
            self.module.warn(text)
            self.assertEqual(str(w[-1].message), text)
            self.assertTrue(w[-1].category is UserWarning)

            self.module.filterwarnings("ignore", "", Warning, "", 0)
            text = 'filtered out'
            self.module.warn(text)
            self.assertNotEqual(str(w[-1].message), text)

            self.module.resetwarnings()
            self.module.filterwarnings("error", "hex*", Warning, "", 0)
            self.assertRaises(UserWarning, self.module.warn, 'hex/oct')
            text = 'nonmatching text'
            self.module.warn(text)
            self.assertEqual(str(w[-1].message), text)
            self.assertTrue(w[-1].category is UserWarning)

class CFilterTests(BaseTest, FilterTests):
    module = c_warnings

class PyFilterTests(BaseTest, FilterTests):
    module = py_warnings


class WarnTests(unittest.TestCase):

    """Test warnings.warn() and warnings.warn_explicit()."""

    def test_message(self):
        with original_warnings.catch_warnings(record=True,
                module=self.module) as w:
            self.module.simplefilter("once")
            for i in range(4):
                text = 'multi %d' %i  # Different text on each call.
                self.module.warn(text)
                self.assertEqual(str(w[-1].message), text)
                self.assertTrue(w[-1].category is UserWarning)

    # Issue 3639
    def test_warn_nonstandard_types(self):
        # warn() should handle non-standard types without issue.
        for ob in (Warning, None, 42):
            with original_warnings.catch_warnings(record=True,
                    module=self.module) as w:
                self.module.simplefilter("once")
                self.module.warn(ob)
                # Don't directly compare objects since
                # ``Warning() != Warning()``.
                self.assertEqual(str(w[-1].message), str(UserWarning(ob)))

    def test_filename(self):
        with warnings_state(self.module):
            with original_warnings.catch_warnings(record=True,
                    module=self.module) as w:
                warning_tests.inner("spam1")
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "warning_tests.py")
                warning_tests.outer("spam2")
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "warning_tests.py")

    def test_stacklevel(self):
        # Test stacklevel argument
        # make sure all messages are different, so the warning won't be skipped
        with warnings_state(self.module):
            with original_warnings.catch_warnings(record=True,
                    module=self.module) as w:
                warning_tests.inner("spam3", stacklevel=1)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "warning_tests.py")
                warning_tests.outer("spam4", stacklevel=1)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "warning_tests.py")

                warning_tests.inner("spam5", stacklevel=2)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "test_warnings.py")
                warning_tests.outer("spam6", stacklevel=2)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "warning_tests.py")
                warning_tests.outer("spam6.5", stacklevel=3)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "test_warnings.py")

                warning_tests.inner("spam7", stacklevel=9999)
                self.assertEqual(os.path.basename(w[-1].filename),
                                    "sys")

    def test_missing_filename_not_main(self):
        # If __file__ is not specified and __main__ is not the module name,
        # then __file__ should be set to the module name.
        filename = warning_tests.__file__
        try:
            del warning_tests.__file__
            with warnings_state(self.module):
                with original_warnings.catch_warnings(record=True,
                        module=self.module) as w:
                    warning_tests.inner("spam8", stacklevel=1)
                    self.assertEqual(w[-1].filename, warning_tests.__name__)
        finally:
            warning_tests.__file__ = filename

    def test_missing_filename_main_with_argv(self):
        # If __file__ is not specified and the caller is __main__ and sys.argv
        # exists, then use sys.argv[0] as the file.
        if not hasattr(sys, 'argv'):
            return
        filename = warning_tests.__file__
        module_name = warning_tests.__name__
        try:
            del warning_tests.__file__
            warning_tests.__name__ = '__main__'
            with warnings_state(self.module):
                with original_warnings.catch_warnings(record=True,
                        module=self.module) as w:
                    warning_tests.inner('spam9', stacklevel=1)
                    self.assertEqual(w[-1].filename, sys.argv[0])
        finally:
            warning_tests.__file__ = filename
            warning_tests.__name__ = module_name

    def test_missing_filename_main_without_argv(self):
        # If __file__ is not specified, the caller is __main__, and sys.argv
        # is not set, then '__main__' is the file name.
        filename = warning_tests.__file__
        module_name = warning_tests.__name__
        argv = sys.argv
        try:
            del warning_tests.__file__
            warning_tests.__name__ = '__main__'
            del sys.argv
            with warnings_state(self.module):
                with original_warnings.catch_warnings(record=True,
                        module=self.module) as w:
                    warning_tests.inner('spam10', stacklevel=1)
                    self.assertEqual(w[-1].filename, '__main__')
        finally:
            warning_tests.__file__ = filename
            warning_tests.__name__ = module_name
            sys.argv = argv

    def test_missing_filename_main_with_argv_empty_string(self):
        # If __file__ is not specified, the caller is __main__, and sys.argv[0]
        # is the empty string, then '__main__ is the file name.
        # Tests issue 2743.
        file_name = warning_tests.__file__
        module_name = warning_tests.__name__
        argv = sys.argv
        try:
            del warning_tests.__file__
            warning_tests.__name__ = '__main__'
            sys.argv = ['']
            with warnings_state(self.module):
                with original_warnings.catch_warnings(record=True,
                        module=self.module) as w:
                    warning_tests.inner('spam11', stacklevel=1)
                    self.assertEqual(w[-1].filename, '__main__')
        finally:
            warning_tests.__file__ = file_name
            warning_tests.__name__ = module_name
            sys.argv = argv

    def test_warn_explicit_type_errors(self):
        # warn_explicit() should error out gracefully if it is given objects
        # of the wrong types.
        # lineno is expected to be an integer.
        self.assertRaises(TypeError, self.module.warn_explicit,
                            None, UserWarning, None, None)
        # Either 'message' needs to be an instance of Warning or 'category'
        # needs to be a subclass.
        self.assertRaises(TypeError, self.module.warn_explicit,
                            None, None, None, 1)
        # 'registry' must be a dict or None.
        self.assertRaises((TypeError, AttributeError),
                            self.module.warn_explicit,
                            None, Warning, None, 1, registry=42)

    def test_bad_str(self):
        # issue 6415
        # Warnings instance with a bad format string for __str__ should not
        # trigger a bus error.
        class BadStrWarning(Warning):
            """Warning with a bad format string for __str__."""
            def __str__(self):
                return ("A bad formatted string %(err)" %
                        {"err" : "there is no %(err)s"})

        with self.assertRaises(ValueError):
            self.module.warn(BadStrWarning())


class CWarnTests(BaseTest, WarnTests):
    module = c_warnings

    # As an early adopter, we sanity check the
    # test.support.import_fresh_module utility function
    def test_accelerated(self):
        self.assertFalse(original_warnings is self.module)
        self.assertFalse(hasattr(self.module.warn, '__code__'))

class PyWarnTests(BaseTest, WarnTests):
    module = py_warnings

    # As an early adopter, we sanity check the
    # test.support.import_fresh_module utility function
    def test_pure_python(self):
        self.assertFalse(original_warnings is self.module)
        self.assertTrue(hasattr(self.module.warn, '__code__'))


class WCmdLineTests(unittest.TestCase):

    def test_improper_input(self):
        # Uses the private _setoption() function to test the parsing
        # of command-line warning arguments
        with original_warnings.catch_warnings(module=self.module):
            self.assertRaises(self.module._OptionError,
                              self.module._setoption, '1:2:3:4:5:6')
            self.assertRaises(self.module._OptionError,
                              self.module._setoption, 'bogus::Warning')
            self.assertRaises(self.module._OptionError,
                              self.module._setoption, 'ignore:2::4:-5')
            self.module._setoption('error::Warning::0')
            self.assertRaises(UserWarning, self.module.warn, 'convert to error')

    def test_improper_option(self):
        # Same as above, but check that the message is printed out when
        # the interpreter is executed. This also checks that options are
        # actually parsed at all.
        rc, out, err = assert_python_ok("-Wxxx", "-c", "pass")
        self.assertIn(b"Invalid -W option ignored: invalid action: 'xxx'", err)

    def test_warnings_bootstrap(self):
        # Check that the warnings module does get loaded when -W<some option>
        # is used (see issue #10372 for an example of silent bootstrap failure).
        rc, out, err = assert_python_ok("-Wi", "-c",
            "import sys; sys.modules['warnings'].warn('foo', RuntimeWarning)")
        # '-Wi' was observed
        self.assertFalse(out.strip())
        self.assertNotIn(b'RuntimeWarning', err)

class CWCmdLineTests(BaseTest, WCmdLineTests):
    module = c_warnings

class PyWCmdLineTests(BaseTest, WCmdLineTests):
    module = py_warnings


class _WarningsTests(BaseTest):

    """Tests specific to the _warnings module."""

    module = c_warnings

    def test_filter(self):
        # Everything should function even if 'filters' is not in warnings.
        with original_warnings.catch_warnings(module=self.module) as w:
            self.module.filterwarnings("error", "", Warning, "", 0)
            self.assertRaises(UserWarning, self.module.warn,
                                'convert to error')
            del self.module.filters
            self.assertRaises(UserWarning, self.module.warn,
                                'convert to error')

    def test_onceregistry(self):
        # Replacing or removing the onceregistry should be okay.
        global __warningregistry__
        message = UserWarning('onceregistry test')
        try:
            original_registry = self.module.onceregistry
            __warningregistry__ = {}
            with original_warnings.catch_warnings(record=True,
                    module=self.module) as w:
                self.module.resetwarnings()
                self.module.filterwarnings("once", category=UserWarning)
                self.module.warn_explicit(message, UserWarning, "file", 42)
                self.assertEqual(w[-1].message, message)
                del w[:]
                self.module.warn_explicit(message, UserWarning, "file", 42)
                self.assertEqual(len(w), 0)
                # Test the resetting of onceregistry.
                self.module.onceregistry = {}
                __warningregistry__ = {}
                self.module.warn('onceregistry test')
                self.assertEqual(w[-1].message.args, message.args)
                # Removal of onceregistry is okay.
                del w[:]
                del self.module.onceregistry
                __warningregistry__ = {}
                self.module.warn_explicit(message, UserWarning, "file", 42)
                self.assertEqual(len(w), 0)
        finally:
            self.module.onceregistry = original_registry

    def test_default_action(self):
        # Replacing or removing defaultaction should be okay.
        message = UserWarning("defaultaction test")
        original = self.module.defaultaction
        try:
            with original_warnings.catch_warnings(record=True,
                    module=self.module) as w:
                self.module.resetwarnings()
                registry = {}
                self.module.warn_explicit(message, UserWarning, "<test>", 42,
                                            registry=registry)
                self.assertEqual(w[-1].message, message)
                self.assertEqual(len(w), 1)
                self.assertEqual(len(registry), 1)
                del w[:]
                # Test removal.
                del self.module.defaultaction
                __warningregistry__ = {}
                registry = {}
                self.module.warn_explicit(message, UserWarning, "<test>", 43,
                                            registry=registry)
                self.assertEqual(w[-1].message, message)
                self.assertEqual(len(w), 1)
                self.assertEqual(len(registry), 1)
                del w[:]
                # Test setting.
                self.module.defaultaction = "ignore"
                __warningregistry__ = {}
                registry = {}
                self.module.warn_explicit(message, UserWarning, "<test>", 44,
                                            registry=registry)
                self.assertEqual(len(w), 0)
        finally:
            self.module.defaultaction = original

    def test_showwarning_missing(self):
        # Test that showwarning() missing is okay.
        text = 'del showwarning test'
        with original_warnings.catch_warnings(module=self.module):
            self.module.filterwarnings("always", category=UserWarning)
            del self.module.showwarning
            with support.captured_output('stderr') as stream:
                self.module.warn(text)
                result = stream.getvalue()
        self.assertIn(text, result)

    def test_showwarning_not_callable(self):
        with original_warnings.catch_warnings(module=self.module):
            self.module.filterwarnings("always", category=UserWarning)
            self.module.showwarning = print
            with support.captured_output('stdout'):
                self.module.warn('Warning!')
            self.module.showwarning = 23
            self.assertRaises(TypeError, self.module.warn, "Warning!")

    def test_show_warning_output(self):
        # With showarning() missing, make sure that output is okay.
        text = 'test show_warning'
        with original_warnings.catch_warnings(module=self.module):
            self.module.filterwarnings("always", category=UserWarning)
            del self.module.showwarning
            with support.captured_output('stderr') as stream:
                warning_tests.inner(text)
                result = stream.getvalue()
        self.assertEqual(result.count('\n'), 2,
                             "Too many newlines in %r" % result)
        first_line, second_line = result.split('\n', 1)
        expected_file = os.path.splitext(warning_tests.__file__)[0] + '.py'
        first_line_parts = first_line.rsplit(':', 3)
        path, line, warning_class, message = first_line_parts
        line = int(line)
        self.assertEqual(expected_file, path)
        self.assertEqual(warning_class, ' ' + UserWarning.__name__)
        self.assertEqual(message, ' ' + text)
        expected_line = '  ' + linecache.getline(path, line).strip() + '\n'
        assert expected_line
        self.assertEqual(second_line, expected_line)

    def test_filename_none(self):
        # issue #12467: race condition if a warning is emitted at shutdown
        globals_dict = globals()
        oldfile = globals_dict['__file__']
        try:
            catch = original_warnings.catch_warnings(record=True,
                                                     module=self.module)
            with catch as w:
                self.module.filterwarnings("always", category=UserWarning)
                globals_dict['__file__'] = None
                original_warnings.warn('test', UserWarning)
                self.assertTrue(len(w))
        finally:
            globals_dict['__file__'] = oldfile


class WarningsDisplayTests(unittest.TestCase):

    """Test the displaying of warnings and the ability to overload functions
    related to displaying warnings."""

    def test_formatwarning(self):
        message = "msg"
        category = Warning
        file_name = os.path.splitext(warning_tests.__file__)[0] + '.py'
        line_num = 3
        file_line = linecache.getline(file_name, line_num).strip()
        format = "%s:%s: %s: %s\n  %s\n"
        expect = format % (file_name, line_num, category.__name__, message,
                            file_line)
        self.assertEqual(expect, self.module.formatwarning(message,
                                                category, file_name, line_num))
        # Test the 'line' argument.
        file_line += " for the win!"
        expect = format % (file_name, line_num, category.__name__, message,
                            file_line)
        self.assertEqual(expect, self.module.formatwarning(message,
                                    category, file_name, line_num, file_line))

    def test_showwarning(self):
        file_name = os.path.splitext(warning_tests.__file__)[0] + '.py'
        line_num = 3
        expected_file_line = linecache.getline(file_name, line_num).strip()
        message = 'msg'
        category = Warning
        file_object = StringIO()
        expect = self.module.formatwarning(message, category, file_name,
                                            line_num)
        self.module.showwarning(message, category, file_name, line_num,
                                file_object)
        self.assertEqual(file_object.getvalue(), expect)
        # Test 'line' argument.
        expected_file_line += "for the win!"
        expect = self.module.formatwarning(message, category, file_name,
                                            line_num, expected_file_line)
        file_object = StringIO()
        self.module.showwarning(message, category, file_name, line_num,
                                file_object, expected_file_line)
        self.assertEqual(expect, file_object.getvalue())

class CWarningsDisplayTests(BaseTest, WarningsDisplayTests):
    module = c_warnings

class PyWarningsDisplayTests(BaseTest, WarningsDisplayTests):
    module = py_warnings


class CatchWarningTests(BaseTest):

    """Test catch_warnings()."""

    def test_catch_warnings_restore(self):
        wmod = self.module
        orig_filters = wmod.filters
        orig_showwarning = wmod.showwarning
        # Ensure both showwarning and filters are restored when recording
        with wmod.catch_warnings(module=wmod, record=True):
            wmod.filters = wmod.showwarning = object()
        self.assertTrue(wmod.filters is orig_filters)
        self.assertTrue(wmod.showwarning is orig_showwarning)
        # Same test, but with recording disabled
        with wmod.catch_warnings(module=wmod, record=False):
            wmod.filters = wmod.showwarning = object()
        self.assertTrue(wmod.filters is orig_filters)
        self.assertTrue(wmod.showwarning is orig_showwarning)

    def test_catch_warnings_recording(self):
        wmod = self.module
        # Ensure warnings are recorded when requested
        with wmod.catch_warnings(module=wmod, record=True) as w:
            self.assertEqual(w, [])
            self.assertTrue(type(w) is list)
            wmod.simplefilter("always")
            wmod.warn("foo")
            self.assertEqual(str(w[-1].message), "foo")
            wmod.warn("bar")
            self.assertEqual(str(w[-1].message), "bar")
            self.assertEqual(str(w[0].message), "foo")
            self.assertEqual(str(w[1].message), "bar")
            del w[:]
            self.assertEqual(w, [])
        # Ensure warnings are not recorded when not requested
        orig_showwarning = wmod.showwarning
        with wmod.catch_warnings(module=wmod, record=False) as w:
            self.assertTrue(w is None)
            self.assertTrue(wmod.showwarning is orig_showwarning)

    def test_catch_warnings_reentry_guard(self):
        wmod = self.module
        # Ensure catch_warnings is protected against incorrect usage
        x = wmod.catch_warnings(module=wmod, record=True)
        self.assertRaises(RuntimeError, x.__exit__)
        with x:
            self.assertRaises(RuntimeError, x.__enter__)
        # Same test, but with recording disabled
        x = wmod.catch_warnings(module=wmod, record=False)
        self.assertRaises(RuntimeError, x.__exit__)
        with x:
            self.assertRaises(RuntimeError, x.__enter__)

    def test_catch_warnings_defaults(self):
        wmod = self.module
        orig_filters = wmod.filters
        orig_showwarning = wmod.showwarning
        # Ensure default behaviour is not to record warnings
        with wmod.catch_warnings(module=wmod) as w:
            self.assertTrue(w is None)
            self.assertTrue(wmod.showwarning is orig_showwarning)
            self.assertTrue(wmod.filters is not orig_filters)
        self.assertTrue(wmod.filters is orig_filters)
        if wmod is sys.modules['warnings']:
            # Ensure the default module is this one
            with wmod.catch_warnings() as w:
                self.assertTrue(w is None)
                self.assertTrue(wmod.showwarning is orig_showwarning)
                self.assertTrue(wmod.filters is not orig_filters)
            self.assertTrue(wmod.filters is orig_filters)

    def test_check_warnings(self):
        # Explicit tests for the test.support convenience wrapper
        wmod = self.module
        if wmod is not sys.modules['warnings']:
            return
        with support.check_warnings(quiet=False) as w:
            self.assertEqual(w.warnings, [])
            wmod.simplefilter("always")
            wmod.warn("foo")
            self.assertEqual(str(w.message), "foo")
            wmod.warn("bar")
            self.assertEqual(str(w.message), "bar")
            self.assertEqual(str(w.warnings[0].message), "foo")
            self.assertEqual(str(w.warnings[1].message), "bar")
            w.reset()
            self.assertEqual(w.warnings, [])

        with support.check_warnings():
            # defaults to quiet=True without argument
            pass
        with support.check_warnings(('foo', UserWarning)):
            wmod.warn("foo")

        with self.assertRaises(AssertionError):
            with support.check_warnings(('', RuntimeWarning)):
                # defaults to quiet=False with argument
                pass
        with self.assertRaises(AssertionError):
            with support.check_warnings(('foo', RuntimeWarning)):
                wmod.warn("foo")

class CCatchWarningTests(CatchWarningTests):
    module = c_warnings

class PyCatchWarningTests(CatchWarningTests):
    module = py_warnings


class EnvironmentVariableTests(BaseTest):

    def test_single_warning(self):
        newenv = os.environ.copy()
        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
        p = subprocess.Popen([sys.executable,
                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
                stdout=subprocess.PIPE, env=newenv)
        self.assertEqual(p.communicate()[0], b"['ignore::DeprecationWarning']")
        self.assertEqual(p.wait(), 0)

    def test_comma_separated_warnings(self):
        newenv = os.environ.copy()
        newenv["PYTHONWARNINGS"] = ("ignore::DeprecationWarning,"
                                    "ignore::UnicodeWarning")
        p = subprocess.Popen([sys.executable,
                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
                stdout=subprocess.PIPE, env=newenv)
        self.assertEqual(p.communicate()[0],
                b"['ignore::DeprecationWarning', 'ignore::UnicodeWarning']")
        self.assertEqual(p.wait(), 0)

    def test_envvar_and_command_line(self):
        newenv = os.environ.copy()
        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
        p = subprocess.Popen([sys.executable, "-W" "ignore::UnicodeWarning",
                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
                stdout=subprocess.PIPE, env=newenv)
        self.assertEqual(p.communicate()[0],
                b"['ignore::UnicodeWarning', 'ignore::DeprecationWarning']")
        self.assertEqual(p.wait(), 0)

    @unittest.skipUnless(sys.getfilesystemencoding() != 'ascii',
                         'requires non-ascii filesystemencoding')
    def test_nonascii(self):
        newenv = os.environ.copy()
        newenv["PYTHONWARNINGS"] = "ignore:DeprecaciónWarning"
        newenv["PYTHONIOENCODING"] = "utf-8"
        p = subprocess.Popen([sys.executable,
                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
                stdout=subprocess.PIPE, env=newenv)
        self.assertEqual(p.communicate()[0],
                "['ignore:DeprecaciónWarning']".encode('utf-8'))
        self.assertEqual(p.wait(), 0)

class CEnvironmentVariableTests(EnvironmentVariableTests):
    module = c_warnings

class PyEnvironmentVariableTests(EnvironmentVariableTests):
    module = py_warnings


class BootstrapTest(unittest.TestCase):
    def test_issue_8766(self):
        # "import encodings" emits a warning whereas the warnings is not loaded
        # or not completely loaded (warnings imports indirectly encodings by
        # importing linecache) yet
        with support.temp_cwd() as cwd, support.temp_cwd('encodings'):
            env = os.environ.copy()
            env['PYTHONPATH'] = cwd

            # encodings loaded by initfsencoding()
            retcode = subprocess.call([sys.executable, '-c', 'pass'], env=env)
            self.assertEqual(retcode, 0)

            # Use -W to load warnings module at startup
            retcode = subprocess.call(
                [sys.executable, '-c', 'pass', '-W', 'always'],
                env=env)
            self.assertEqual(retcode, 0)

def test_main():
    py_warnings.onceregistry.clear()
    c_warnings.onceregistry.clear()
    support.run_unittest(
        CFilterTests, PyFilterTests,
        CWarnTests, PyWarnTests,
        CWCmdLineTests, PyWCmdLineTests,
        _WarningsTests,
        CWarningsDisplayTests, PyWarningsDisplayTests,
        CCatchWarningTests, PyCatchWarningTests,
        CEnvironmentVariableTests, PyEnvironmentVariableTests,
        BootstrapTest,
    )


if __name__ == "__main__":
    test_main()