Allow positional arguments tox -e system-tests.

CONTRIBUTING.rst

@@ -140,10 +140,17 @@ Running System Tests
 - To run system tests you can execute::
 
    $ tox -e system-tests
+   $ tox -e system-tests3
 
   or run only system tests for a particular package via::
 
    $ python system_tests/run_system_test.py --package {package}
+   $ python3 system_tests/run_system_test.py --package {package}
+
+  To run a subset of the system tests::
+
+   $ tox -e system-tests -- datastore storage
+   $ python system_tests/attempt_system_tests.py datastore storage
 
   This alone will not run the tests. You'll need to change some local
   auth settings and change some configuration in your project to
@@ -243,6 +250,7 @@ Running System Tests
 - To run the system tests with the ``pubsub`` emulator::
 
    $ tox -e pubsub-emulator
+   $ GOOGLE_CLOUD_DISABLE_GRPC=true tox -e pubsub-emulator
 
   If you'd like to run them directly (outside of a ``tox`` environment), first
   start the emulator and take note of the process ID::

system_tests/attempt_system_tests.py

@@ -44,6 +44,8 @@
 """
 
 
+from __future__ import print_function
+import argparse
 import os
 import subprocess
 import sys
@@ -54,6 +56,7 @@
 from run_system_test import run_module_tests
 
 
+BIGTABLE_API = 'bigtable'
 MODULES = (  # ordered from most to least stable
     'datastore',
     'storage',
@@ -63,15 +66,15 @@
     'logging',
     'translate',
     'monitoring',
+    BIGTABLE_API,
 )
-if sys.version_info[:2] == (2, 7):
-    MODULES += ('bigtable',)
 
 SCRIPTS_DIR = os.path.dirname(__file__)
 ROOT_DIR = os.path.abspath(os.path.join(SCRIPTS_DIR, '..'))
 ENCRYPTED_KEYFILE = os.path.join(ROOT_DIR, 'system_tests', 'key.json.enc')
 ENCRYPTED_KEY_ENV = 'encrypted_c16407eb06cc_key'
 ENCRYPTED_INIT_VECTOR_ENV = 'encrypted_c16407eb06cc_iv'
+ALL_MODULES = object()  # Sentinel for argparser
 
 
 def check_environment():
@@ -136,11 +139,49 @@ def prepare_to_run():
     decrypt_keyfile()
 
 
+def get_parser():
+    """Get an argument parser to determine a list of packages."""
+    parser = argparse.ArgumentParser(
+        description='google-cloud tests runner.')
+    help_msg = ('List of packages to be tested. '
+                'If left blank, tests all packages.')
+    parser.add_argument('packages', nargs='*',
+                        default=ALL_MODULES, help=help_msg)
+    return parser
+
+
+def get_modules():
+    """Get the list of modules names to run system tests for."""
+    parser = get_parser()
+    args = parser.parse_args()
+    if args.packages is ALL_MODULES:
+        result = list(MODULES)
+        if sys.version_info[:2] != (2, 7):
+            result.remove(BIGTABLE_API)
+    else:
+        result = []
+        invalid = []
+        for package in args.packages:
+            if package in MODULES:
+                result.append(package)
+            else:
+                invalid.append(package)
+
+        if invalid:
+            msg = 'No system test for packages: ' + ', '.join(invalid)
+            print(msg, file=sys.stderr)
+            sys.exit(1)
+
+    return result
+
+
 def main():
     """Run all the system tests if necessary."""
     prepare_to_run()
+
     failed_modules = 0
-    for module in MODULES:
+    modules = get_modules()
+    for module in modules:
         try:
             run_module_tests(module)
         except FailedSystemTestModule:

tox.ini

@@ -60,7 +60,8 @@ passenv = {[testenv:system-tests]passenv}
 basepython =
     python2.7
 commands =
-    python -c "import shutil; shutil.rmtree('docs/_build/json', ignore_errors=True)"
+    python -c \
+        "import shutil; shutil.rmtree('docs/_build/json', ignore_errors=True)"
     {toxinidir}/scripts/update_json_docs.sh
 deps =
     parinx
@@ -78,7 +79,8 @@ passenv =
 basepython =
     python2.7
 commands =
-    python -c "import shutil; shutil.rmtree('docs/_build', ignore_errors=True)"
+    python -c \
+        "import shutil; shutil.rmtree('docs/_build', ignore_errors=True)"
     sphinx-build -W -b html -d docs/_build/doctrees docs docs/_build/html
     python {toxinidir}/scripts/verify_included_modules.py --build-root _build
 deps =
@@ -88,7 +90,10 @@ deps =
 passenv = {[testenv:system-tests]passenv} SPHINX_RELEASE READTHEDOCS
 
 [pep8]
-exclude = docs/conf.py,google/cloud/bigtable/_generated*/*,google/cloud/datastore/_generated/*
+exclude =
+    docs/conf.py,
+    google/cloud/bigtable/_generated*/*,
+    google/cloud/datastore/_generated/*
 verbose = 1
 
 [testenv:lint]
@@ -107,14 +112,14 @@ passenv = {[testenv:system-tests]passenv}
 basepython =
     python2.7
 commands =
-    python {toxinidir}/system_tests/attempt_system_tests.py
+    python {toxinidir}/system_tests/attempt_system_tests.py {posargs}
 passenv = GOOGLE_* GOOGLE_CLOUD_* TRAVIS* encrypted_*
 
 [testenv:system-tests3]
 basepython =
     python3.4
 commands =
-    python {toxinidir}/system_tests/attempt_system_tests.py
+    python {toxinidir}/system_tests/attempt_system_tests.py {posargs}
 passenv = {[testenv:system-tests]passenv}
 
 [testenv:datastore-emulator]