Add import-time tests for psutil

Two new tests that validate:

1) that psutil can be sucessfuly reload()'d
2) that a missing procfs doesn't prevent importing, or
   correct functionality on linux.

3 files changed, 73 insertions, 3 deletions

diff --git a/psutil/__init__.py b/psutil/__init__.py
index 90ce5baf..32eab7b1 100644
--- a/psutil/__init__.py
+++ b/psutil/__init__.py
@@ -108,7 +108,6 @@ if sys.platform.startswith("linux"):
             RLIMIT_SIGPENDING = _psutil_linux.RLIMIT_SIGPENDING
         except AttributeError:
             pass
-        del _psutil_linux
 
 elif sys.platform.startswith("win32"):
     from . import _pswindows as _psplatform
diff --git a/test/_linux.py b/test/_linux.py
index 5e7d10a7..d2125cec 100644
--- a/test/_linux.py
+++ b/test/_linux.py
@@ -15,6 +15,7 @@ import io
 import os
 import pprint
 import re
+import shutil
 import socket
 import struct
 import sys
@@ -34,6 +35,7 @@ from psutil._compat import u
 from test_psutil import call_until
 from test_psutil import get_kernel_version
 from test_psutil import get_test_subprocess
+from test_psutil import importlib
 from test_psutil import LINUX
 from test_psutil import MEMORY_TOLERANCE
 from test_psutil import POSIX
@@ -44,7 +46,6 @@ from test_psutil import TRAVIS
 from test_psutil import unittest
 from test_psutil import which
 
-
 HERE = os.path.abspath(os.path.dirname(__file__))
 # procps-ng 3.3.10 changed the output format of free
 # and removed the 'buffers/cache line'
@@ -472,6 +473,65 @@ class LinuxSpecificTestCase(unittest.TestCase):
             psutil.PROCFS_PATH = "/proc"
             os.rmdir(tdir)
 
+    def test_no_procfs_for_import(self):
+        my_procfs = tempfile.mkdtemp()
+
+        with open(os.path.join(my_procfs, 'stat'), 'w') as f:
+            f.write('cpu   0 0 0 0 0 0 0 0 0 0\n')
+            f.write('cpu0  0 0 0 0 0 0 0 0 0 0\n')
+            f.write('cpu1  0 0 0 0 0 0 0 0 0 0\n')
+
+        try:
+            orig_open = open
+
+            def open_mock(name, *args):
+                if name.startswith('/proc'):
+                    raise IOError(errno.ENOENT, 'rejecting access for test')
+                return orig_open(name, *args)
+            patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+            with mock.patch(patch_point, side_effect=open_mock):
+                importlib.reload(psutil)
+
+                self.assertRaises(IOError, psutil.cpu_times)
+                self.assertRaises(IOError, psutil.cpu_times, percpu=True)
+                self.assertRaises(IOError, psutil.cpu_percent)
+                self.assertRaises(IOError, psutil.cpu_percent, percpu=True)
+                self.assertRaises(IOError, psutil.cpu_times_percent)
+                self.assertRaises(
+                    IOError, psutil.cpu_times_percent, percpu=True)
+
+                psutil.PROCFS_PATH = my_procfs
+
+                self.assertEqual(psutil.cpu_percent(), 0)
+                self.assertEqual(sum(psutil.cpu_times_percent()), 0)
+
+                # since we don't know the number of CPUs at import time,
+                # we awkwardly say there are none until the second call
+                per_cpu_percent = psutil.cpu_percent(percpu=True)
+                self.assertEqual(sum(per_cpu_percent), 0)
+
+                # ditto awkward length
+                per_cpu_times_percent = psutil.cpu_times_percent(percpu=True)
+                self.assertEqual(sum(map(sum, per_cpu_times_percent)), 0)
+
+                # much user, very busy
+                with open(os.path.join(my_procfs, 'stat'), 'w') as f:
+                    f.write('cpu   1 0 0 0 0 0 0 0 0 0\n')
+                    f.write('cpu0  1 0 0 0 0 0 0 0 0 0\n')
+                    f.write('cpu1  1 0 0 0 0 0 0 0 0 0\n')
+
+                self.assertNotEqual(psutil.cpu_percent(), 0)
+                self.assertNotEqual(
+                    sum(psutil.cpu_percent(percpu=True)), 0)
+                self.assertNotEqual(sum(psutil.cpu_times_percent()), 0)
+                self.assertNotEqual(
+                    sum(map(sum, psutil.cpu_times_percent(percpu=True))), 0)
+        finally:
+            shutil.rmtree(my_procfs)
+            importlib.reload(psutil)
+
+        self.assertEqual(psutil.PROCFS_PATH, '/proc')
+
     @unittest.skipUnless(
         get_kernel_version() >= (2, 6, 36),
         "prlimit() not available on this Linux kernel version")
diff --git a/test/test_psutil.py b/test/test_psutil.py
index d2a85713..0435256b 100644
--- a/test/test_psutil.py
+++ b/test/test_psutil.py
@@ -22,8 +22,8 @@ import contextlib
 import datetime
 import errno
 import functools
-import imp
 import json
+import imp
 import os
 import pickle
 import pprint
@@ -71,6 +71,14 @@ if sys.version_info >= (3, 4):
 else:
     enum = None
 
+if PY3:
+    import importlib
+    # python <=3.3
+    if not hasattr(importlib, 'reload'):
+        import imp as importlib
+else:
+    import imp as importlib
+
 
 # ===================================================================
 # --- Constants
@@ -3200,6 +3208,9 @@ class TestUnicode(unittest.TestCase):
         self.assertIsInstance(path, str)
         self.assertEqual(os.path.normcase(path), os.path.normcase(self.uexe))
 
+    def test_psutil_is_reloadable(self):
+        importlib.reload(psutil)
+
 
 def main():
     tests = []