Allow to use capsys and capfd in other fixtures

Fix #2709
This commit is contained in:
Bruno Oliveira 2017-09-26 02:34:41 -03:00
parent de0d19ca09
commit 9919269ed0
3 changed files with 95 additions and 19 deletions

View File

@ -61,6 +61,18 @@ def pytest_load_initial_conftests(early_config, parser, args):
class CaptureManager:
"""
Capture plugin, manages that the appropriate capture method is enabled/disabled during collection and each
test phase (setup, call, teardown). After each of those points, the captured output is obtained and
attached to the collection/runtest report.
There are two levels of capture:
* global: which is enabled by default and can be suppressed by the ``-s`` option. This is always enabled/disabled
during collection and each test phase.
* fixture: when a test function or one of its fixture depend on the ``capsys`` or ``capfd`` fixtures. In this
case special handling is needed to ensure the fixtures take precedence over the global capture.
"""
def __init__(self, method):
self._method = method
@ -88,8 +100,9 @@ class CaptureManager:
def resumecapture(self):
self._capturing.resume_capturing()
def suspendcapture(self, in_=False):
self.deactivate_funcargs()
def suspendcapture(self, item=None, in_=False):
if item is not None:
self.deactivate_fixture(item)
cap = getattr(self, "_capturing", None)
if cap is not None:
try:
@ -98,16 +111,19 @@ class CaptureManager:
cap.suspend_capturing(in_=in_)
return outerr
def activate_funcargs(self, pyfuncitem):
capfuncarg = pyfuncitem.__dict__.pop("_capfuncarg", None)
if capfuncarg is not None:
capfuncarg._start()
self._capfuncarg = capfuncarg
def activate_fixture(self, item):
"""If the current item is using ``capsys`` or ``capfd``, activate them so they take precedence over
the global capture.
"""
fixture = getattr(item, "_capture_fixture", None)
if fixture is not None:
fixture._start()
def deactivate_funcargs(self):
capfuncarg = self.__dict__.pop("_capfuncarg", None)
if capfuncarg is not None:
capfuncarg.close()
def deactivate_fixture(self, item):
"""Deactivates the ``capsys`` or ``capfd`` fixture of this item, if any."""
fixture = getattr(item, "_capture_fixture", None)
if fixture is not None:
fixture.close()
@pytest.hookimpl(hookwrapper=True)
def pytest_make_collect_report(self, collector):
@ -126,20 +142,25 @@ class CaptureManager:
@pytest.hookimpl(hookwrapper=True)
def pytest_runtest_setup(self, item):
self.resumecapture()
# no need to activate a capture fixture because they activate themselves during creation; this
# only makes sense when a fixture uses a capture fixture, otherwise the capture fixture will
# be activated during pytest_runtest_call
yield
self.suspendcapture_item(item, "setup")
@pytest.hookimpl(hookwrapper=True)
def pytest_runtest_call(self, item):
self.resumecapture()
self.activate_funcargs(item)
# it is important to activate this fixture during the call phase so it overwrites the "global"
# capture
self.activate_fixture(item)
yield
# self.deactivate_funcargs() called from suspendcapture()
self.suspendcapture_item(item, "call")
@pytest.hookimpl(hookwrapper=True)
def pytest_runtest_teardown(self, item):
self.resumecapture()
self.activate_fixture(item)
yield
self.suspendcapture_item(item, "teardown")
@ -152,7 +173,7 @@ class CaptureManager:
self.reset_capturings()
def suspendcapture_item(self, item, when, in_=False):
out, err = self.suspendcapture(in_=in_)
out, err = self.suspendcapture(item, in_=in_)
item.add_report_section(when, "stdout", out)
item.add_report_section(when, "stderr", err)
@ -168,8 +189,8 @@ def capsys(request):
"""
if "capfd" in request.fixturenames:
raise request.raiseerror(error_capsysfderror)
request.node._capfuncarg = c = CaptureFixture(SysCapture, request)
return c
with _install_capture_fixture_on_item(request, SysCapture) as fixture:
yield fixture
@pytest.fixture
@ -181,9 +202,29 @@ def capfd(request):
if "capsys" in request.fixturenames:
request.raiseerror(error_capsysfderror)
if not hasattr(os, 'dup'):
pytest.skip("capfd funcarg needs os.dup")
request.node._capfuncarg = c = CaptureFixture(FDCapture, request)
return c
pytest.skip("capfd fixture needs os.dup function which is not available in this system")
with _install_capture_fixture_on_item(request, FDCapture) as fixture:
yield fixture
@contextlib.contextmanager
def _install_capture_fixture_on_item(request, capture_class):
"""
Context manager which creates a ``CaptureFixture`` instance and "installs" it on
the item/node of the given request. Used by ``capsys`` and ``capfd``.
The CaptureFixture is added as attribute of the item because it needs to accessed
by ``CaptureManager`` during its ``pytest_runtest_*`` hooks.
"""
request.node._capture_fixture = fixture = CaptureFixture(capture_class, request)
capmanager = request.config.pluginmanager.getplugin('capturemanager')
# need to active this fixture right away in case it is being used by another fixture (setup phase)
# if this fixture is being used only by a test function (call phase), then we wouldn't need this
# activation, but it doesn't hurt
capmanager.activate_fixture(request.node)
yield fixture
fixture.close()
del request.node._capture_fixture
class CaptureFixture:

1
changelog/2709.bugfix Normal file
View File

@ -0,0 +1 @@
``capsys`` and ``capfd`` can now be used by other fixtures.

View File

@ -517,6 +517,40 @@ class TestCaptureFixture(object):
assert 'captured before' not in result.stdout.str()
assert 'captured after' not in result.stdout.str()
@pytest.mark.parametrize('fixture', ['capsys', 'capfd'])
def test_fixture_use_by_other_fixtures(self, testdir, fixture):
"""
Ensure that capsys and capfd can be used by other fixtures during setup and teardown.
"""
testdir.makepyfile("""
from __future__ import print_function
import sys
import pytest
@pytest.fixture
def captured_print({fixture}):
print('stdout contents begin')
print('stderr contents begin', file=sys.stderr)
out, err = {fixture}.readouterr()
yield out, err
print('stdout contents end')
print('stderr contents end', file=sys.stderr)
out, err = {fixture}.readouterr()
assert out == 'stdout contents end\\n'
assert err == 'stderr contents end\\n'
def test_captured_print(captured_print):
out, err = captured_print
assert out == 'stdout contents begin\\n'
assert err == 'stderr contents begin\\n'
""".format(fixture=fixture))
result = testdir.runpytest_subprocess()
result.stdout.fnmatch_lines("*1 passed*")
assert 'stdout contents begin' not in result.stdout.str()
assert 'stderr contents begin' not in result.stdout.str()
def test_setup_failure_does_not_kill_capturing(testdir):
sub1 = testdir.mkpydir("sub1")