Enabled parallel testing by default in runtests.py.

django/db/backends/base/features.py

@@ -212,6 +212,10 @@ class BaseDatabaseFeatures(object):
     # every expression is null?
     greatest_least_ignores_nulls = False
 
+    # Can the backend clone databases for parallel test execution?
+    # Defaults to False to allow third-party backends to opt-in.
+    can_clone_databases = False
+
     def __init__(self, connection):
         self.connection = connection
 

django/db/backends/mysql/features.py

@@ -31,6 +31,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     can_release_savepoints = True
     atomic_transactions = False
     supports_column_check_constraints = False
+    can_clone_databases = True
 
     @cached_property
     def _mysql_storage_engine(self):

django/db/backends/postgresql/features.py

@@ -28,3 +28,4 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     has_case_insensitive_like = False
     requires_sqlparse_for_splitting = False
     greatest_least_ignores_nulls = True
+    can_clone_databases = True

django/db/backends/sqlite3/features.py

@@ -37,6 +37,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     can_rollback_ddl = True
     supports_paramstyle_pyformat = False
     supports_sequence_reset = False
+    can_clone_databases = True
 
     @cached_property
     def uses_savepoints(self):

docs/internals/contributing/writing-code/unit-tests.txt

@@ -284,3 +284,16 @@ combine this with ``--verbosity=2``, all SQL queries will be output::
 .. versionadded:: 1.8
 
     The ``--reverse`` and ``--debug-sql`` options were added.
+
+By default tests are run in parallel with one process per core. You can adjust
+this behavior with the ``--parallel`` option::
+
+    $ ./runtests.py basic --parallel=1
+
+You can also use the ``DJANGO_TEST_PROCESSES`` environment variable for this
+purpose.
+
+.. versionadded:: 1.9
+
+    Support for running tests in parallel and the ``--parallel`` option were
+    added.

docs/releases/1.9.txt

@@ -135,6 +135,10 @@ Each process gets its own database. You must ensure that different test cases
 don't access the same resources. For instance, test cases that touch the
 filesystem should create a temporary directory for their own use.
 
+This option is enabled by default for Django's own test suite on database
+backends that support it (this is all the built-in backends except for
+Oracle).
+
 Minor features
 ~~~~~~~~~~~~~~
 
@@ -686,7 +690,8 @@ Database backend API
   and hasn't been called anywhere in Django's code or tests.
 
 * In order to support test parallelization, you must implement the
-  ``DatabaseCreation._clone_test_db()`` method. You may have to adjust
+  ``DatabaseCreation._clone_test_db()`` method and set
+  ``DatabaseFeatures.can_clone_databases = True``. You may have to adjust
   ``DatabaseCreation.get_test_db_clone_settings()``.
 
 Default settings that were tuples are now lists

tests/requirements/base.txt

@@ -8,3 +8,4 @@ PyYAML
 pytz > dev
 selenium
 sqlparse
+tblib

tests/runtests.py

@@ -12,7 +12,7 @@ from argparse import ArgumentParser
 import django
 from django.apps import apps
 from django.conf import settings
-from django.db import connection
+from django.db import connection, connections
 from django.test import TestCase, TransactionTestCase
 from django.test.runner import default_test_processes
 from django.test.utils import get_runner
@@ -103,8 +103,10 @@ def get_installed():
 
 def setup(verbosity, test_labels, parallel):
     if verbosity >= 1:
-        print("Testing against Django installed in '%s' with %d processes" % (
-            os.path.dirname(django.__file__), parallel))
+        msg = "Testing against Django installed in '%s'" % os.path.dirname(django.__file__)
+        if parallel > 1:
+            msg += " with %d processes" % parallel
+        print(msg)
 
     # Force declaring available_apps in TransactionTestCase for faster tests.
     def no_available_apps(self):
@@ -232,6 +234,17 @@ def teardown(state):
         setattr(settings, key, value)
 
 
+def actual_test_processes(parallel):
+    if parallel == 0:
+        # This doesn't work before django.setup() on some databases.
+        if all(conn.features.can_clone_databases for conn in connections.all()):
+            return default_test_processes()
+        else:
+            return 1
+    else:
+        return parallel
+
+
 def django_tests(verbosity, interactive, failfast, keepdb, reverse,
                  test_labels, debug_sql, parallel):
     state = setup(verbosity, test_labels, parallel)
@@ -249,7 +262,7 @@ def django_tests(verbosity, interactive, failfast, keepdb, reverse,
         keepdb=keepdb,
         reverse=reverse,
         debug_sql=debug_sql,
-        parallel=parallel,
+        parallel=actual_test_processes(parallel),
     )
     failures = test_runner.run_tests(
         test_labels or get_installed(),
@@ -396,7 +409,7 @@ if __name__ == "__main__":
         '--debug-sql', action='store_true', dest='debug_sql', default=False,
         help='Turn on the SQL query logger within tests.')
     parser.add_argument(
-        '--parallel', dest='parallel', nargs='?', default=1, type=int,
+        '--parallel', dest='parallel', nargs='?', default=0, type=int,
         const=default_test_processes(),
         help='Run tests in parallel processes.')