ETL TESTING

ETL basically stands for Extract Transform Load - which simply implies the process where you extract data from Source Tables, transform them in to the desired format based on certain rules and finally load them onto Target tables. There are numerous tools that help you with ETL process - Informatica, Control-M being a few notable ones.

So ETL Testing implies - Testing this entire process using a tool or at table level with the help of test cases and Rules Mapping document.

In ETL Testing, the following are validated -
1) Data File loads from Source system on to Source Tables.
2) The ETL Job that is designed to extract data from Source tables and then move them to staging tables. (Transform process)
3) Data validation within the Staging tables to check all Mapping Rules / Transformation Rules are followed.
4) Data Validation within Target tables to ensure data is present in required format and there is no data loss from Source to Target tables.

  Both ETL and Database Testing are same..Whatever we achieve with Data Warehouse can be achieved by Database also...We all know that data warehouse is nothing but the set of databases which follows some characterstics like : subject oriented,Non Volatile,Integrated and Time Varient.


The only difference is that
1) The data in database is Normalized in Nature and the datra in DWH is Denormalized in Nature.
2) Database Testing uses ER Model whereas DWH uses Dimensional Modeling technique.
3) Database Testing is done on OLTP system and DWH testing is done on OLAP systems.
4) Database uses only .sql files whereas ETL/DWH can use any type of file to import data.