REF/TST: replace capture_stderr with pytest capsys fixture (#24496)

Author: simonjayhawkins

pandas/tests/indexes/datetimes/test_datetime.py

@@ -1,5 +1,4 @@
 from datetime import date
-import sys
 
 import dateutil
 import numpy as np
@@ -125,15 +124,14 @@ def test_map(self):
         exp = Index([f(x) for x in rng], dtype='<U8')
         tm.assert_index_equal(result, exp)
 
-    @tm.capture_stderr
-    def test_map_fallthrough(self):
+    def test_map_fallthrough(self, capsys):
         # GH#22067, check we don't get warnings about silently ignored errors
         dti = date_range('2017-01-01', '2018-01-01', freq='B')
 
         dti.map(lambda x: pd.Period(year=x.year, month=x.month, freq='M'))
 
-        cv = sys.stderr.getvalue()
-        assert cv == ''
+        captured = capsys.readouterr()
+        assert captured.err == ''
 
     def test_iteration_preserves_tz(self):
         # see gh-8890

pandas/tests/io/parser/test_c_parser_only.py

@@ -10,7 +10,6 @@
 from io import TextIOWrapper
 import mmap
 import os
-import sys
 import tarfile
 
 import numpy as np
@@ -449,8 +448,7 @@ def test_data_after_quote(c_parser_only):
     tm.assert_frame_equal(result, expected)
 
 
-@tm.capture_stderr
-def test_comment_whitespace_delimited(c_parser_only):
+def test_comment_whitespace_delimited(c_parser_only, capsys):
     parser = c_parser_only
     test_input = """\
 1 2
@@ -466,10 +464,10 @@ def test_comment_whitespace_delimited(c_parser_only):
     df = parser.read_csv(StringIO(test_input), comment="#", header=None,
                          delimiter="\\s+", skiprows=0,
                          error_bad_lines=False)
-    error = sys.stderr.getvalue()
+    captured = capsys.readouterr()
     # skipped lines 2, 3, 4, 9
     for line_num in (2, 3, 4, 9):
-        assert "Skipping line {}".format(line_num) in error, error
+        assert "Skipping line {}".format(line_num) in captured.err
     expected = DataFrame([[1, 2],
                           [5, 2],
                           [6, 2],

pandas/tests/io/parser/test_common.py

@@ -1867,8 +1867,7 @@ def test_error_bad_lines(all_parsers, kwargs, warn_kwargs):
         parser.read_csv(StringIO(data), **kwargs)
 
 
-@tm.capture_stderr
-def test_warn_bad_lines(all_parsers):
+def test_warn_bad_lines(all_parsers, capsys):
     # see gh-15925
     parser = all_parsers
     data = "a\n1\n1,2,3\n4\n5,6,7"
@@ -1879,13 +1878,12 @@ def test_warn_bad_lines(all_parsers):
                              warn_bad_lines=True)
     tm.assert_frame_equal(result, expected)
 
-    val = sys.stderr.getvalue()
-    assert "Skipping line 3" in val
-    assert "Skipping line 5" in val
+    captured = capsys.readouterr()
+    assert "Skipping line 3" in captured.err
+    assert "Skipping line 5" in captured.err
 
 
-@tm.capture_stderr
-def test_suppress_error_output(all_parsers):
+def test_suppress_error_output(all_parsers, capsys):
     # see gh-15925
     parser = all_parsers
     data = "a\n1\n1,2,3\n4\n5,6,7"
@@ -1896,8 +1894,8 @@ def test_suppress_error_output(all_parsers):
                              warn_bad_lines=False)
     tm.assert_frame_equal(result, expected)
 
-    val = sys.stderr.getvalue()
-    assert val == ""
+    captured = capsys.readouterr()
+    assert captured.err == ""
 
 
 def test_read_table_deprecated(all_parsers):

pandas/tests/io/parser/test_python_parser_only.py

@@ -8,7 +8,6 @@
 """
 
 import csv
-import sys
 
 import pytest
 
@@ -248,8 +247,7 @@ def fail_read():
         fail_read()
 
 
-@tm.capture_stderr
-def test_none_delimiter(python_parser_only):
+def test_none_delimiter(python_parser_only, capsys):
     # see gh-13374 and gh-17465
     parser = python_parser_only
     data = "a,b,c\n0,1,2\n3,4,5,6\n7,8,9"
@@ -263,8 +261,8 @@ def test_none_delimiter(python_parser_only):
                              error_bad_lines=False)
     tm.assert_frame_equal(result, expected)
 
-    warning = sys.stderr.getvalue()
-    assert "Skipping line 3" in warning
+    captured = capsys.readouterr()
+    assert "Skipping line 3" in captured.err
 
 
 @pytest.mark.parametrize("data", [

pandas/tests/io/parser/test_textreader.py

@@ -6,7 +6,6 @@
 """
 
 import os
-import sys
 
 import numpy as np
 from numpy import nan
@@ -135,8 +134,7 @@ def test_integer_thousands_alt(self):
         expected = DataFrame([123456, 12500])
         tm.assert_frame_equal(result, expected)
 
-    @tm.capture_stderr
-    def test_skip_bad_lines(self):
+    def test_skip_bad_lines(self, capsys):
         # too many lines, see #2430 for why
         data = ('a:b:c\n'
                 'd:e:f\n'
@@ -164,10 +162,10 @@ def test_skip_bad_lines(self):
                             error_bad_lines=False,
                             warn_bad_lines=True)
         reader.read()
-        val = sys.stderr.getvalue()
+        captured = capsys.readouterr()
 
-        assert 'Skipping line 4' in val
-        assert 'Skipping line 6' in val
+        assert 'Skipping line 4' in captured.err
+        assert 'Skipping line 6' in captured.err
 
     def test_header_not_enough_lines(self):
         data = ('skip this\n'

pandas/tests/series/test_repr.py

@@ -2,7 +2,6 @@
 # pylint: disable-msg=E1101,W0612
 
 from datetime import datetime, timedelta
-import sys
 
 import numpy as np
 
@@ -121,15 +120,14 @@ def test_tidy_repr(self):
         a.name = 'title1'
         repr(a)  # should not raise exception
 
-    @tm.capture_stderr
-    def test_repr_bool_fails(self):
+    def test_repr_bool_fails(self, capsys):
         s = Series([DataFrame(np.random.randn(2, 2)) for i in range(5)])
 
         # It works (with no Cython exception barf)!
         repr(s)
 
-        output = sys.stderr.getvalue()
-        assert output == ''
+        captured = capsys.readouterr()
+        assert captured.err == ''
 
     def test_repr_name_iterable_indexable(self):
         s = Series([1, 2, 3], name=np.int64(3))

pandas/util/testing.py

@@ -684,52 +684,6 @@ def wrapper(*args, **kwargs):
     return wrapper
 
 
-def capture_stderr(f):
-    r"""
-    Decorator to capture stderr in a buffer so that it can be checked
-    (or suppressed) during testing.
-
-    Parameters
-    ----------
-    f : callable
-        The test that is capturing stderr.
-
-    Returns
-    -------
-    f : callable
-        The decorated test ``f``, which captures stderr.
-
-    Examples
-    --------
-
-    >>> from pandas.util.testing import capture_stderr
-    >>> import sys
-    >>>
-    >>> @capture_stderr
-    ... def test_stderr_pass():
-    ...     sys.stderr.write("foo")
-    ...     out = sys.stderr.getvalue()
-    ...     assert out == "foo\n"
-    >>>
-    >>> @capture_stderr
-    ... def test_stderr_fail():
-    ...     sys.stderr.write("foo")
-    ...     out = sys.stderr.getvalue()
-    ...     assert out == "bar\n"
-    ...
-    AssertionError: assert 'foo\n' == 'bar\n'
-    """
-
-    @compat.wraps(f)
-    def wrapper(*args, **kwargs):
-        try:
-            sys.stderr = StringIO()
-            f(*args, **kwargs)
-        finally:
-            sys.stderr = sys.__stderr__
-
-    return wrapper
-
 # -----------------------------------------------------------------------------
 # Console debugging tools
 

scripts/tests/test_validate_docstrings.py

@@ -4,7 +4,6 @@
 import textwrap
 import pytest
 import numpy as np
-from pandas.util.testing import capture_stderr
 import validate_docstrings
 validate_one = validate_docstrings.validate_one
 
@@ -739,36 +738,32 @@ def _import_path(self, klass=None, func=None):
 
         return base_path
 
-    @capture_stderr
-    def test_good_class(self):
+    def test_good_class(self, capsys):
         errors = validate_one(self._import_path(
             klass='GoodDocStrings'))['errors']
         assert isinstance(errors, list)
         assert not errors
 
-    @capture_stderr
     @pytest.mark.parametrize("func", [
         'plot', 'sample', 'random_letters', 'sample_values', 'head', 'head1',
         'contains', 'mode', 'good_imports'])
-    def test_good_functions(self, func):
+    def test_good_functions(self, capsys, func):
         errors = validate_one(self._import_path(
             klass='GoodDocStrings', func=func))['errors']
         assert isinstance(errors, list)
         assert not errors
 
-    @capture_stderr
-    def test_bad_class(self):
+    def test_bad_class(self, capsys):
         errors = validate_one(self._import_path(
             klass='BadGenericDocStrings'))['errors']
         assert isinstance(errors, list)
         assert errors
 
-    @capture_stderr
     @pytest.mark.parametrize("func", [
         'func', 'astype', 'astype1', 'astype2', 'astype3', 'plot', 'method',
         'private_classes',
     ])
-    def test_bad_generic_functions(self, func):
+    def test_bad_generic_functions(self, capsys, func):
         errors = validate_one(self._import_path(  # noqa:F821
             klass='BadGenericDocStrings', func=func))['errors']
         assert isinstance(errors, list)