Fixed #18271 -- Changed stage at which TransactionTestCase flushes DB tables.

Previously, the flush was done before the test case execution and now
it is performed after it.

Other changes to the testing infrastructure include:

* TransactionTestCase now doesn't reset autoincrement sequences either
  (previous behavior can achieved by using `reset_sequences`.)
  With this, no implicit such reset is performed by any of the provided
  TestCase classes.

* New ordering of test cases: All unittest tes cases are run first and
  doctests are run at the end.

THse changes could be backward-incompatible with test cases that relied
on some kind of state being preserved between tests. Please read the
relevant sections of the release notes and testing documentation for
further details.

Thanks Andreas Pelme for the initial patch. Karen Tracey and Anssi
Kääriäinen for the feedback and Anssi for reviewing.

This also fixes #12408.

8 files changed, 111 insertions, 61 deletions

diff --git a/django/core/management/commands/flush.py b/django/core/management/commands/flush.py
index 2fc2e7ed26..ac7b7a3599 100644
--- a/django/core/management/commands/flush.py
+++ b/django/core/management/commands/flush.py
@@ -29,6 +29,8 @@ class Command(NoArgsCommand):
         connection = connections[db]
         verbosity = int(options.get('verbosity'))
         interactive = options.get('interactive')
+        # 'reset_sequences' is a stealth option
+        reset_sequences = options.get('reset_sequences', True)
 
         self.style = no_style()
 
@@ -40,7 +42,7 @@ class Command(NoArgsCommand):
             except ImportError:
                 pass
 
-        sql_list = sql_flush(self.style, connection, only_django=True)
+        sql_list = sql_flush(self.style, connection, only_django=True, reset_sequences=reset_sequences)
 
         if interactive:
             confirm = raw_input("""You have requested a flush of the database.
diff --git a/django/core/management/sql.py b/django/core/management/sql.py
index 46d3cf28ed..7579cbe8ab 100644
--- a/django/core/management/sql.py
+++ b/django/core/management/sql.py
@@ -98,7 +98,7 @@ def sql_delete(app, style, connection):
 
     return output[::-1] # Reverse it, to deal with table dependencies.
 
-def sql_flush(style, connection, only_django=False):
+def sql_flush(style, connection, only_django=False, reset_sequences=True):
     """
     Returns a list of the SQL statements used to flush the database.
 
@@ -109,9 +109,8 @@ def sql_flush(style, connection, only_django=False):
         tables = connection.introspection.django_table_names(only_existing=True)
     else:
         tables = connection.introspection.table_names()
-    statements = connection.ops.sql_flush(
-        style, tables, connection.introspection.sequence_list()
-    )
+    seqs = connection.introspection.sequence_list() if reset_sequences else ()
+    statements = connection.ops.sql_flush(style, tables, seqs)
     return statements
 
 def sql_custom(app, style, connection):
diff --git a/django/db/backends/__init__.py b/django/db/backends/__init__.py
index a896f5fd08..6e23ad5bb5 100644
--- a/django/db/backends/__init__.py
+++ b/django/db/backends/__init__.py
@@ -748,11 +748,24 @@ class BaseDatabaseOperations(object):
         the given database tables (without actually removing the tables
         themselves).
 
+        The returned value also includes SQL statements required to reset DB
+        sequences passed in :param sequences:.
+
         The `style` argument is a Style object as returned by either
         color_style() or no_style() in django.core.management.color.
         """
         raise NotImplementedError()
 
+    def sequence_reset_by_name_sql(self, style, sequences):
+        """
+        Returns a list of the SQL statements required to reset sequences
+        passed in :param sequences:.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+        """
+        return []
+
     def sequence_reset_sql(self, style, model_list):
         """
         Returns a list of the SQL statements required to reset sequences for
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index ec65207ed8..2222f89cf0 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -262,22 +262,25 @@ class DatabaseOperations(BaseDatabaseOperations):
             for table in tables:
                 sql.append('%s %s;' % (style.SQL_KEYWORD('TRUNCATE'), style.SQL_FIELD(self.quote_name(table))))
             sql.append('SET FOREIGN_KEY_CHECKS = 1;')
-
-            # Truncate already resets the AUTO_INCREMENT field from
-            # MySQL version 5.0.13 onwards. Refs #16961.
-            if self.connection.mysql_version < (5,0,13):
-                sql.extend(
-                    ["%s %s %s %s %s;" % \
-                     (style.SQL_KEYWORD('ALTER'),
-                      style.SQL_KEYWORD('TABLE'),
-                      style.SQL_TABLE(self.quote_name(sequence['table'])),
-                      style.SQL_KEYWORD('AUTO_INCREMENT'),
-                      style.SQL_FIELD('= 1'),
-                     ) for sequence in sequences])
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
             return sql
         else:
             return []
 
+    def sequence_reset_by_name_sql(self, style, sequences):
+        # Truncate already resets the AUTO_INCREMENT field from
+        # MySQL version 5.0.13 onwards. Refs #16961.
+        if self.connection.mysql_version < (5, 0, 13):
+            return ["%s %s %s %s %s;" % \
+                    (style.SQL_KEYWORD('ALTER'),
+                    style.SQL_KEYWORD('TABLE'),
+                    style.SQL_TABLE(self.quote_name(sequence['table'])),
+                    style.SQL_KEYWORD('AUTO_INCREMENT'),
+                    style.SQL_FIELD('= 1'),
+                    ) for sequence in sequences]
+        else:
+            return []
+
     def validate_autopk_value(self, value):
         # MySQLism: zero in AUTO_INCREMENT field does not work. Refs #17653.
         if value == 0:
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 32ae420ce0..b08113fed7 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -298,18 +298,23 @@ WHEN (new.%(col_name)s IS NULL)
                     for table in tables]
             # Since we've just deleted all the rows, running our sequence
             # ALTER code will reset the sequence to 0.
-            for sequence_info in sequences:
-                sequence_name = self._get_sequence_name(sequence_info['table'])
-                table_name = self.quote_name(sequence_info['table'])
-                column_name = self.quote_name(sequence_info['column'] or 'id')
-                query = _get_sequence_reset_sql() % {'sequence': sequence_name,
-                                                     'table': table_name,
-                                                     'column': column_name}
-                sql.append(query)
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
             return sql
         else:
             return []
 
+    def sequence_reset_by_name_sql(self, style, sequences):
+        sql = []
+        for sequence_info in sequences:
+            sequence_name = self._get_sequence_name(sequence_info['table'])
+            table_name = self.quote_name(sequence_info['table'])
+            column_name = self.quote_name(sequence_info['column'] or 'id')
+            query = _get_sequence_reset_sql() % {'sequence': sequence_name,
+                                                    'table': table_name,
+                                                    'column': column_name}
+            sql.append(query)
+        return sql
+
     def sequence_reset_sql(self, style, model_list):
         from django.db import models
         output = []
diff --git a/django/db/backends/postgresql_psycopg2/operations.py b/django/db/backends/postgresql_psycopg2/operations.py
index e93a15512b..40fe629110 100644
--- a/django/db/backends/postgresql_psycopg2/operations.py
+++ b/django/db/backends/postgresql_psycopg2/operations.py
@@ -85,25 +85,29 @@ class DatabaseOperations(BaseDatabaseOperations):
                 (style.SQL_KEYWORD('TRUNCATE'),
                     style.SQL_FIELD(', '.join([self.quote_name(table) for table in tables]))
             )]
-
-            # 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL statements
-            # to reset sequence indices
-            for sequence_info in sequences:
-                table_name = sequence_info['table']
-                column_name = sequence_info['column']
-                if not (column_name and len(column_name) > 0):
-                    # This will be the case if it's an m2m using an autogenerated
-                    # intermediate table (see BaseDatabaseIntrospection.sequence_list)
-                    column_name = 'id'
-                sql.append("%s setval(pg_get_serial_sequence('%s','%s'), 1, false);" % \
-                    (style.SQL_KEYWORD('SELECT'),
-                    style.SQL_TABLE(self.quote_name(table_name)),
-                    style.SQL_FIELD(column_name))
-                )
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
             return sql
         else:
             return []
 
+    def sequence_reset_by_name_sql(self, style, sequences):
+        # 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL statements
+        # to reset sequence indices
+        sql = []
+        for sequence_info in sequences:
+            table_name = sequence_info['table']
+            column_name = sequence_info['column']
+            if not (column_name and len(column_name) > 0):
+                # This will be the case if it's an m2m using an autogenerated
+                # intermediate table (see BaseDatabaseIntrospection.sequence_list)
+                column_name = 'id'
+            sql.append("%s setval(pg_get_serial_sequence('%s','%s'), 1, false);" % \
+                (style.SQL_KEYWORD('SELECT'),
+                style.SQL_TABLE(self.quote_name(table_name)),
+                style.SQL_FIELD(column_name))
+            )
+        return sql
+
     def tablespace_sql(self, tablespace, inline=False):
         if inline:
             return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
diff --git a/django/test/simple.py b/django/test/simple.py
index 4f05284543..bf0219d53f 100644
--- a/django/test/simple.py
+++ b/django/test/simple.py
@@ -5,7 +5,7 @@ from django.core.exceptions import ImproperlyConfigured
 from django.db.models import get_app, get_apps
 from django.test import _doctest as doctest
 from django.test.utils import setup_test_environment, teardown_test_environment
-from django.test.testcases import OutputChecker, DocTestRunner, TestCase
+from django.test.testcases import OutputChecker, DocTestRunner
 from django.utils import unittest
 from django.utils.importlib import import_module
 from django.utils.module_loading import module_has_submodule
@@ -263,7 +263,7 @@ class DjangoTestSuiteRunner(object):
             for test in extra_tests:
                 suite.addTest(test)
 
-        return reorder_suite(suite, (TestCase,))
+        return reorder_suite(suite, (unittest.TestCase,))
 
     def setup_databases(self, **kwargs):
         from django.db import connections, DEFAULT_DB_ALIAS
diff --git a/django/test/testcases.py b/django/test/testcases.py
index b9aae21e8e..b60188bf30 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -23,6 +23,7 @@ from django.core import mail
 from django.core.exceptions import ValidationError, ImproperlyConfigured
 from django.core.handlers.wsgi import WSGIHandler
 from django.core.management import call_command
+from django.core.management.color import no_style
 from django.core.signals import request_started
 from django.core.servers.basehttp import (WSGIRequestHandler, WSGIServer,
     WSGIServerException)
@@ -444,10 +445,15 @@ class SimpleTestCase(ut2.TestCase):
 
 
 class TransactionTestCase(SimpleTestCase):
+
     # The class we'll use for the test client self.client.
     # Can be overridden in derived classes.
     client_class = Client
 
+    # Subclasses can ask for resetting of auto increment sequence before each
+    # test case
+    reset_sequences = False
+
     def _pre_setup(self):
         """Performs any pre-test setup. This includes:
 
@@ -462,22 +468,36 @@ class TransactionTestCase(SimpleTestCase):
         self._urlconf_setup()
         mail.outbox = []
 
+    def _reset_sequences(self, db_name):
+        conn = connections[db_name]
+        if conn.features.supports_sequence_reset:
+            sql_list = \
+                conn.ops.sequence_reset_by_name_sql(no_style(),
+                                                    conn.introspection.sequence_list())
+            if sql_list:
+                try:
+                    cursor = conn.cursor()
+                    for sql in sql_list:
+                        cursor.execute(sql)
+                except Exception:
+                    transaction.rollback_unless_managed(using=db_name)
+                    raise
+                transaction.commit_unless_managed(using=db_name)
+
     def _fixture_setup(self):
-        # If the test case has a multi_db=True flag, flush all databases.
-        # Otherwise, just flush default.
-        if getattr(self, 'multi_db', False):
-            databases = connections
-        else:
-            databases = [DEFAULT_DB_ALIAS]
-        for db in databases:
-            call_command('flush', verbosity=0, interactive=False, database=db,
-                         skip_validation=True)
+        # If the test case has a multi_db=True flag, act on all databases.
+        # Otherwise, just on the default DB.
+        db_names = connections if getattr(self, 'multi_db', False) else [DEFAULT_DB_ALIAS]
+        for db_name in db_names:
+            # Reset sequences
+            if self.reset_sequences:
+                self._reset_sequences(db_name)
 
             if hasattr(self, 'fixtures'):
                 # We have to use this slightly awkward syntax due to the fact
                 # that we're using *args and **kwargs together.
                 call_command('loaddata', *self.fixtures,
-                             **{'verbosity': 0, 'database': db, 'skip_validation': True})
+                             **{'verbosity': 0, 'database': db_name, 'skip_validation': True})
 
     def _urlconf_setup(self):
         if hasattr(self, 'urls'):
@@ -534,7 +554,12 @@ class TransactionTestCase(SimpleTestCase):
             conn.close()
 
     def _fixture_teardown(self):
-        pass
+        # If the test case has a multi_db=True flag, flush all databases.
+        # Otherwise, just flush default.
+        databases = connections if getattr(self, 'multi_db', False) else [DEFAULT_DB_ALIAS]
+        for db in databases:
+            call_command('flush', verbosity=0, interactive=False, database=db,
+                         skip_validation=True, reset_sequences=False)
 
     def _urlconf_teardown(self):
         if hasattr(self, '_old_root_urlconf'):
@@ -808,22 +833,21 @@ class TestCase(TransactionTestCase):
         if not connections_support_transactions():
             return super(TestCase, self)._fixture_setup()
 
+        assert not self.reset_sequences, 'reset_sequences cannot be used on TestCase instances'
+
         # If the test case has a multi_db=True flag, setup all databases.
         # Otherwise, just use default.
-        if getattr(self, 'multi_db', False):
-            databases = connections
-        else:
-            databases = [DEFAULT_DB_ALIAS]
+        db_names = connections if getattr(self, 'multi_db', False) else [DEFAULT_DB_ALIAS]
 
-        for db in databases:
-            transaction.enter_transaction_management(using=db)
-            transaction.managed(True, using=db)
+        for db_name in db_names:
+            transaction.enter_transaction_management(using=db_name)
+            transaction.managed(True, using=db_name)
         disable_transaction_methods()
 
         from django.contrib.sites.models import Site
         Site.objects.clear_cache()
 
-        for db in databases:
+        for db in db_names:
             if hasattr(self, 'fixtures'):
                 call_command('loaddata', *self.fixtures,
                              **{