Pytest/capsys fixture not capturing stdout

[derwolfe]

Py.test isn't capturing the output from stdout or stderr.

import sys

stdout = sys.stdout

def test_use_logger(capsys):
    stdout.write("called")
    out, err = capsys.readouterr()
    assert "called" in out

The test case was run and reproduced on OS X 10.11 with pythons 2.7.10 and 3.5.0.

The versions used are:

py==1.4.30
pytest==2.8.2

Thanks!

[derwolfe]

Also, calling sys.stdout.write and sys.stderr.write directly do seem to work correctly (that is, their output is captured).

[RonnyPfannschmidt]

capsys will replace the actual object instead of the underlying file descriptor
making a reference to the prior object will of course replace the stream

a solution is in planning, but will at best it 3.0

[The-Compiler]

As @RonnyPfannschmidt said, you're "saving" sys.stdout before pytest can replace it with the capturing one. The solution pretty much boils down to "don't do that" 😉

Can this be closed?

[derwolfe]

@RonnyPfannschmidt thanks for your response. Yes, this can be closed.