ETL testing is made easier when a testing strategy is well defined. The ETL testing process goes through different phases, as illustrated below: 

• Analyze Business Requirements: To perform ETL Testing effectively, it is crucial to understand and capture the business requirements through the use of data models, business FLOW diagrams, reports, etc.
• Identifying and Validating Data Source: To proceed, it is necessary to identify the source data and perform preliminary checks such as schema checks, table counts, and table validations. The purpose of this is to make sure the ETL process matches the business model specification.
• Design Test Cases and Preparing Test Data: Step three includes designing ETL mapping scenarios, developing SQL scripts, and defining transformation RULES. Lastly, verifying the documents against business needs to make sure they cater to those needs. As soon as all the test cases have been checked and approved, the pre-execution check is performed. All three steps of our ETL processes - namely extracting, transforming, and loading - are covered by test cases.
• Test Execution with Bug Reporting and Closure: This process continues until the exit criteria (business requirements) have been met. In the previous step, if any defects were found, they were sent to the developer for fixing, after which retesting was performed. MOREOVER, regression testing is performed in order to prevent the introduction of new bugs during the FIX of an earlier bug.
• Summary Report and Result Analysis: At this step, a test report is prepared, which lists the test cases and their status (passed or failed). As a result of this report, stakeholders or decision-makers will be able to properly maintain the DELIVERY threshold by understanding the bug and the result of the testing process.
• Test Closure: Once everything is completed, the reports are closed.