Added a common database backend implementation.

Added sqlite (proof of concept)

persistence/implementation/sqlite/tests/util/clean_db.e

@@ -0,0 +1,66 @@
+note
+	description: "[
+		    Setting up database tests
+			1. Put the database in a known state before running your test suite.
+			2. Data reinitialization. For testing in developer sandboxes, something that you should do every time you rebuild the system, you may want to forgo dropping and rebuilding the database in favor of simply reinitializing the source data. 
+				You can do this either by erasing all existing data and then inserting the initial data vales back into the database, or you can simple run updates to reset the data values. 
+			   	The first approach is less risky and may even be faster for large amounts of data. - See more at: http://www.agiledata.org/essays/databaseTesting.html#sthash.6yVp35g8.dpuf
+		]"
+
+	date: "$Date$"
+	revision: "$Revision$"
+	EIS: "name=Database Testing", "src=http://www.agiledata.org/essays/databaseTesting.html", "protocol=uri"
+
+class
+	CLEAN_DB
+
+feature
+
+	clean_db (a_connection: DATABASE_CONNECTION)
+			-- Clean db test.
+		local
+			l_parameters: STRING_TABLE[STRING]
+		do
+			create l_parameters.make (0)
+
+			db_handler(a_connection).set_query (create {DATABASE_QUERY}.data_reader (Sql_delete_nodes, l_parameters))
+			db_handler(a_connection).execute_change
+
+				-- Clean Users
+			db_handler(a_connection).set_query (create {DATABASE_QUERY}.data_reader (Sql_delete_users, l_parameters))
+			db_handler(a_connection).execute_change
+
+--				-- Reset Autoincremente
+--			db_handler(a_connection).set_query (create {DATABASE_QUERY}.data_reader (Rest_users_autoincrement, l_parameters))
+--			db_handler(a_connection).execute_change
+
+--			db_handler(a_connection).set_query (create {DATABASE_QUERY}.data_reader (Rest_nodes_autoincrement, l_parameters))
+--			db_handler(a_connection).execute_change
+		end
+
+
+
+feature -- Database Hanlder
+
+	db_handler (a_connection: DATABASE_CONNECTION): DATABASE_HANDLER
+			-- Db handler
+		once
+			create {DATABASE_HANDLER_IMPL} Result.make (a_connection)
+		end
+
+
+feature -- Sql delete queries
+
+	Sql_delete_users: STRING = "delete from Users"
+		-- Clean Users.
+
+	Sql_delete_nodes: STRING = "delete from Nodes"
+		-- Clean Nodes.
+
+	Rest_users_autoincrement: STRING = "ALTER TABLE Users AUTO_INCREMENT = 1"
+		-- reset autoincrement
+
+	Rest_nodes_autoincrement: STRING = "ALTER TABLE Nodes AUTO_INCREMENT = 1"
+		-- reset autoincrement.
+
+end