diff --git a/system_tests/run_system_test.py b/system_tests/run_system_test.py
index 612c35c967d5..ab284ed5936c 100644
--- a/system_tests/run_system_test.py
+++ b/system_tests/run_system_test.py
@@ -20,12 +20,18 @@
 # repository root is the current directory.
 from system_tests import system_test_utils
 
+REQUIREMENTS = {
+    'datastore': ['dataset_id', 'credentials'],
+    'storage': ['project', 'credentials'],
+    'pubsub': ['project', 'credentials'],
+}
+
 
 def get_parser():
     parser = argparse.ArgumentParser(
         description='GCloud test runner against actual project.')
     parser.add_argument('--package', dest='package',
-                        choices=('datastore', 'storage', 'pubsub'),
+                        choices=REQUIREMENTS.keys(),
                         default='datastore', help='Package to be tested.')
     return parser
 
@@ -41,14 +47,9 @@ def main():
     parser = get_parser()
     args = parser.parse_args()
     # Make sure environ is set before running test.
-    if args.package == 'datastore':
-        system_test_utils.check_environ(require_datastore=True)
-    elif args.package == 'storage':
-        system_test_utils.check_environ(require_storage=True)
-    elif args.package == 'pubsub':
-        system_test_utils.check_environ(require_pubsub=True)
-    else:
-        raise ValueError('Unexpected package name.')
+    requirements = REQUIREMENTS[args.package]
+    system_test_utils.check_environ(*requirements)
+
     test_result = run_module_tests(args.package)
     if not test_result.wasSuccessful():
         sys.exit(1)
diff --git a/system_tests/system_test_utils.py b/system_tests/system_test_utils.py
index 4d497b8020d4..0c8425ea742f 100644
--- a/system_tests/system_test_utils.py
+++ b/system_tests/system_test_utils.py
@@ -16,7 +16,7 @@
 import os
 import sys
 
-from gcloud.environment_vars import CREDENTIALS
+from gcloud.environment_vars import CREDENTIALS as TEST_CREDENTIALS
 from gcloud.environment_vars import TESTS_DATASET
 from gcloud.environment_vars import TESTS_PROJECT
 
@@ -24,22 +24,32 @@
 # From shell environ. May be None.
 PROJECT_ID = os.getenv(TESTS_PROJECT)
 DATASET_ID = os.getenv(TESTS_DATASET)
-CREDENTIALS = os.getenv(CREDENTIALS)
+CREDENTIALS = os.getenv(TEST_CREDENTIALS)
 
 ENVIRON_ERROR_MSG = """\
 To run the system tests, you need to set some environment variables.
 Please check the CONTRIBUTING guide for instructions.
+
+Missing variables: %s
 """
 
 
-def check_environ(require_datastore=False, require_storage=False,
-                  require_pubsub=False):
-    if require_datastore:
-        if DATASET_ID is None or not os.path.isfile(CREDENTIALS):
-            print(ENVIRON_ERROR_MSG, file=sys.stderr)
-            sys.exit(1)
+def check_environ(*requirements):
+
+    missing = []
+
+    if 'dataset_id' in requirements:
+        if DATASET_ID is None:
+            missing.append(TESTS_DATASET)
+
+    if 'project' in requirements:
+        if PROJECT_ID is None:
+            missing.append(TESTS_PROJECT)
+
+    if 'credentials' in requirements:
+        if CREDENTIALS is None or not os.path.isfile(CREDENTIALS):
+            missing.append(TEST_CREDENTIALS)
 
-    if require_storage or require_pubsub:
-        if PROJECT_ID is None or not os.path.isfile(CREDENTIALS):
-            print(ENVIRON_ERROR_MSG, file=sys.stderr)
-            sys.exit(1)
+    if missing:
+        print(ENVIRON_ERROR_MSG % ', '.join(missing), file=sys.stderr)
+        sys.exit(1)