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.

4 files changed, 60 insertions, 35 deletions

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)