added a test for stdout capturing and fixed two problems with the win…

…dows tests

sacred/stdout_capturing.py

@@ -3,15 +3,14 @@
 from __future__ import division, print_function, unicode_literals
 import os
 import sys
-from io import StringIO
 import subprocess
 from threading import Timer
 from contextlib import contextmanager
 import wrapt
 from sacred.optional import libc
 from tempfile import NamedTemporaryFile
 from sacred.settings import SETTINGS
-from sacred.utils import FileNotFoundError
+from sacred.utils import FileNotFoundError, StringIO
 
 
 __sacred__ = True  # marks files that should be filtered from stack traces
@@ -110,11 +109,13 @@ def tee_output_fd():
                 ['tee', '-a', '/dev/stderr'], preexec_fn=os.setsid,
                 stdin=subprocess.PIPE, stderr=target_fd, stdout=2)
         except (FileNotFoundError, OSError):
+            # No tee found in this operating system. Trying to use a python
+            # implementation of tee. However this is slow and error-prone.
             tee_stdout = subprocess.Popen(
-                [sys.executable, "-m", "sacred.pytee"], preexec_fn=os.setsid,
+                [sys.executable, "-m", "sacred.pytee"],
                 stdin=subprocess.PIPE, stderr=target_fd)
             tee_stderr = subprocess.Popen(
-                [sys.executable, "-m", "sacred.pytee"], preexec_fn=os.setsid,
+                [sys.executable, "-m", "sacred.pytee"],
                 stdin=subprocess.PIPE, stdout=target_fd)
 
         flush()

sacred/utils.py

@@ -22,9 +22,11 @@
     class FileNotFoundError(IOError):
         def __init__(self, msg):
             super(FileNotFoundError, self).__init__(errno.ENOENT, msg)
+    from StringIO import StringIO
 else:
     # Reassign so that we can import it from here
     FileNotFoundError = FileNotFoundError
+    from io import StringIO
 
 NO_LOGGER = logging.getLogger('ignore')
 NO_LOGGER.disabled = 1
@@ -303,7 +305,8 @@ def apply_backspaces_and_linefeeds(text):
     Interpret text like a terminal by removing backspace and linefeed
     characters and applying them line by line.
 
-    If final line ends with a carriage it keeps it to be concatanable with next output chunk
+    If final line ends with a carriage it keeps it to be concatenable with next
+    output chunk.
     """
     orig_lines = text.split('\n')
     orig_lines_len = len(orig_lines)
@@ -312,12 +315,15 @@ def apply_backspaces_and_linefeeds(text):
         chars, cursor = [], 0
         orig_line_len = len(orig_line)
         for orig_char_idx, orig_char in enumerate(orig_line):
-            if orig_char == '\r' and (orig_char_idx != orig_line_len - 1 or orig_line_idx != orig_lines_len - 1):
+            if orig_char == '\r' and (orig_char_idx != orig_line_len - 1 or
+                                      orig_line_idx != orig_lines_len - 1):
                 cursor = 0
             elif orig_char == '\b':
                 cursor = max(0, cursor - 1)
             else:
-                if orig_char == '\r' and orig_char_idx == orig_line_len - 1 and orig_line_idx == orig_lines_len - 1:
+                if (orig_char == '\r' and
+                        orig_char_idx == orig_line_len - 1 and
+                        orig_line_idx == orig_lines_len - 1):
                     cursor = len(chars)
                 if cursor == len(chars):
                     chars.append(orig_char)

tests/test_run.py

@@ -225,6 +225,21 @@ def test_unobserved_run_doesnt_emit(run):
     assert not observer.failed_event.called
 
 
+@pytest.mark.parametrize("capture_mode", ["no", "sys", "fd"])
+def test_stdout_capturing(run, capsys, capture_mode):
+    def print_mock_progress():
+        for i in range(10):
+            print(i, end="")
+        sys.stdout.flush()
+
+    run.main_function.side_effect = print_mock_progress
+    run.capture_mode = capture_mode
+    with capsys.disabled():
+        run()
+    if capture_mode != "no":
+        assert run.captured_out == '0123456789'
+
+
 def test_captured_out_filter(run, capsys):
     def print_mock_progress():
         sys.stdout.write('progress 0')