allow capture to output while also storing the data internally (like tee)

[sangmeshcp]

when i run the test case i have lot of logs which use logger and print in my testcase.. i need mechanism where i can print all the logs while its being executed on screen and capture it to a file descriptor simultaneously .

pytest -s test.py (pytest --capture=no test.py )

when I run the logs are printed to sys.stdout which is right ..

what I'm looking for is

pytest --capture=no,fd

this will ensure i can see what is happening while the test is being executed and the logs are written to the fd which is a file.

example :

$ pytest --capture=no test.py 
============================================================= test session starts =============================================================
platform linux -- Python 3.4.3, pytest-3.0.7, py-1.4.32, pluggy-0.4.0
rootdir: /tmp, inifile:
collected 8 items 

printing testing 123 123 123 from test.. 
None
.



------------------------------------------------------------- Test Summary Begin --------------------------------------------------------------
test.py::test::()::                    : Passed   

-------------------------------------------------------------- Test Summary End ---------------------------------------------------------------

the output "printing testing 123 123 123 from test.. " need to written to file as well

[nicoddemus]

IIUC, you want pytest to capture stdout and simultaneously print it to screen and write it to a file?

[sangmeshcp]

@nicoddemus yes exactly

[nicoddemus]

OK thanks for clarifying.

[RonnyPfannschmidt]

i would propose a py.test --capure=tee_fd

[sangmeshcp]

any update on this ?? anybody implementing this proposal

[RonnyPfannschmidt]

@sangmeshcp atm im not aware of anyone having the volunteering time availiable atm,

would you like to try, we def can give guidance, but it will be a while before we can tackle this ourselfes

[dnut]

One of these answers recommends monkey patching pytest to implement this use case:
https://stackoverflow.com/questions/14405063/how-can-i-see-normal-print-output-created-during-pytest-run
Maybe this can be adapted to add a new option to pytest?

[nicoddemus]

I just remembered that the internal pastebin does exactly that:

pytest/_pytest/pastebin.py

Lines 17 to 36 in 4cb60da

	@pytest.hookimpl(trylast=True)
	def pytest_configure(config):
	import py
	if config.option.pastebin == "all":
	tr = config.pluginmanager.getplugin('terminalreporter')
	# if no terminal reporter plugin is present, nothing we can do here;
	# this can happen when this function executes in a slave node
	# when using pytest-xdist, for example
	if tr is not None:
	# pastebin file will be utf-8 encoded binary file
	config._pastebinfile = tempfile.TemporaryFile('w+b')
	oldwrite = tr._tw.write
	def tee_write(s, **kwargs):
	oldwrite(s, **kwargs)
	if py.builtin._istext(s):
	s = s.encode('utf-8')
	config._pastebinfile.write(s)
	tr._tw.write = tee_write

This definitely could be done by the terminal writer based on an option, like --tee=file.txt (which could even be used multiple times).

Seems simple to do, if anyone wants to try it we can give guidance. 👍

[RonnyPfannschmidt]

at second glance however, the implementation is incorrect for capture

[nicoddemus]

at second glance however, the implementation is incorrect for capture

You are right, it only works for things pytest is writing out to the terminal. If we do implement the --tee feature (or whatever it is called) we should also update this pastebin code.

[dhood]

Am I correct in thinking that this has been closed by #3176?

[nicoddemus]

@dhood thanks for the heads up, but #3176 deals only if no capture, stdout or stderr should be displayed when tests fail. This issue is about capturing stdout and stderr, and also display it in the terminal and write it into a file at the same time.