Correct timeout to check every so often

src/_pytest/pytester.py

@@ -1086,6 +1086,8 @@ class Testdir(object):
             else:
                 end = time.time() + timeout
 
+                resolution = min(0.1, timeout / 10)
+
                 while True:
                     ret = popen.poll()
                     if ret is not None:
@@ -1095,7 +1097,7 @@ class Testdir(object):
                     if remaining <= 0:
                         handle_timeout()
 
-                    time.sleep(remaining * 0.9)
+                    time.sleep(resolution)
         finally:
             f1.close()
             f2.close()

testing/test_pytester.py

@@ -4,6 +4,7 @@ import os
 import py.path
 import pytest
 import sys
+import time
 import _pytest.pytester as pytester
 from _pytest.pytester import HookRecorder
 from _pytest.pytester import CwdSnapshot, SysModulesSnapshot, SysPathsSnapshot
@@ -408,6 +409,18 @@ def test_testdir_run_no_timeout(testdir):
     assert testdir.runpytest_subprocess(testfile).ret == EXIT_OK
 
 
+def test_testdir_run_with_timeout(testdir):
+    testfile = testdir.makepyfile("def test_no_timeout(): pass")
+
+    start = time.time()
+    result = testdir.runpytest_subprocess(testfile, timeout=10)
+    end = time.time()
+    duration = end - start
+
+    assert result.ret == EXIT_OK
+    assert duration < 1
+
+
 def test_testdir_run_timeout_expires(testdir):
     testfile = testdir.makepyfile(
         """