[test] introduce db_version helper

Author: kares

test/db/mysql/connection_test.rb

@@ -6,7 +6,6 @@ def test_mysql_strict_mode_disabled
     run_without_connection do |orig_connection|
       ActiveRecord::Base.establish_connection(orig_connection.merge(:strict => false))
       sql_mode = select_rows("SELECT @@SESSION.sql_mode")
-      db_version = ActiveRecord::Base.connection.database_version
       if db_version > "5.6"
         assert ! sql_mode.flatten.include?("STRICT_ALL_TABLES")
       else

test/db/mysql/test_helper.rb

@@ -22,6 +22,11 @@ def mariadb_driver?; end unless defined? JRUBY_VERSION
   def mariadb_server?; connection.send(:mariadb?) end
   alias mariadb? mariadb_server?
 
+  def database_version
+    ActiveRecord::Base.connection.database_version
+  end
+  alias db_version database_version
+
 end
 
 class Test::Unit::TestCase