tests: Improve unit tests runtime performance

This patch set does 2 things:

1) Improves unit test runtime peformance via pytest-xdist [0]
2) Reduces finnicky nature of `is_connected` helpers which
   sometimes skip even when there is access to the internet;
   logic has been added to make these checks more accurate
   to avoid skipping tests

Note that while there are newer alternatives to pytest-xdist they
are only compatible with much newer versions of Python.

[0] https://pypi.org/project/pytest-xdist/

Change-Id: Ib04b48ebabca0551058e5e1065056f4e559fbfe6

test-requirements.txt

@@ -2,6 +2,7 @@
 pytest==3.2.1
 pytest-cov==2.5.1
 testfixtures
+pytest-xdist==1.23.2
 mock==2.0.0
 
 # Formatting

tests/unit/conftest.py

@@ -12,13 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import atexit
 import copy
-
 import os
-import pytest
 import shutil
 import tempfile
 
+import pytest
+
 from pegleg import config
 """Fixtures that are applied to all unit tests."""
 
@@ -35,7 +36,10 @@ def restore_config():
         config.GLOBAL_CONTEXT = original_global_context
 
 
-@pytest.fixture(scope="module", autouse=True)
+# NOTE(felipemonteiro): This uses `atexit` rather than a `pytest.fixture`
+# decorator because 1) this only needs to be run exactly once and 2) this
+# works across multiple test executors via `pytest -n <num_cores>`
+@atexit.register
 def clean_temporary_git_repos():
     """Iterates through all temporarily created directories and deletes each
     one that was created for testing.
@@ -51,8 +55,5 @@ def clean_temporary_git_repos():
                 if any(p.startswith('airship') for p in os.listdir(path)):
                     yield path
 
-    try:
+    for tempdir in temporary_git_repos():
-        yield
+        shutil.rmtree(tempdir, ignore_errors=True)
-    finally:
-        for tempdir in temporary_git_repos():
-            shutil.rmtree(tempdir, ignore_errors=True)

tests/unit/test_utils.py

@@ -55,11 +55,14 @@ def is_connected():
 
     :returns: True if connected else False.
     """
-    try:
+    for _ in range(3):
-        r = requests.get("http://www.github.com/", proxies={}, timeout=3)
+        try:
-        return r.ok
+            r = requests.get("http://www.github.com/", proxies={}, timeout=3)
-    except requests.exceptions.RequestException:
+            r.raise_for_status()
-        return False
+            return True
+        except requests.exceptions.RequestException:
+            pass
+    return False
 
 
 def is_connected_behind_proxy():
@@ -67,9 +70,12 @@ def is_connected_behind_proxy():
 
     :returns: True if connected else False.
     """
-    try:
+    for _ in range(3):
-        r = requests.get(
+        try:
-            "http://www.github.com/", proxies=_PROXY_SERVERS, timeout=3)
+            r = requests.get(
-        return r.ok
+                "http://www.github.com/", proxies=_PROXY_SERVERS, timeout=3)
-    except requests.exceptions.RequestException:
+            r.raise_for_status()
-        return False
+            return True
+        except requests.exceptions.RequestException:
+            pass
+    return False

tools/gate/run-unit-tests.sh

@@ -2,9 +2,11 @@
 
 set -e
 posargs=$@
+# cross-platform way to derive the number of logical cores
+readonly num_cores=$(python -c 'import multiprocessing as mp; print(mp.cpu_count())')
 if [ ${#posargs} -ge 1 ]; then
-    pytest -k  ${posargs}
+    pytest -k ${posargs} -n $num_cores
 else
-    pytest
+    pytest -n $num_cores
 fi
 set +e