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What is ETL Testing & its Importance

October 10, 2017
ETL Testing, ETL Testing Tutorials, ETL Testing Tools

ETL Testing is the process of testing associated with the Data Warehousing projects. This testing mechanism is necessary when a bulk of data is transferred from one place to another. For big enterprises, it is a frequent process to move data from one location to another for data integration and data migration processes. ETL testing is a data-centric process which ensures that the entire data has transferred and located in the destination without fail. 

Before discussing ETL Testing the 2 important aspects should be known:

  • Business Intelligence is the process of collecting raw data (ie.the records of the daily transactions of an organization) and formulating these data to the meaningful information such as reports, graphs etc…
  • Data Warehousing is the process of managing a Data Warehouse.A Data Warehouse is a logical collection of all the data from an Enterprise’s various resources. A Data Warehouse is developed by integrating data from several resources and designed for query and analysis.Hence the data is turned into high-quality information for every level of reporting requirements.

What is ETL

ETL stands for Extract-Transform-Load. For Large enterprises, data is extracted from the Databases transformed as per the data warehouse structure and loaded to the data warehouses. The above process should be tested effectively for ensuring the effective management of data in Data Warehouse.

ETL Testing

ETL  Testing is the testing technique which helps to test the extraction of data for the transformation, verification of data at the transformation stages and loading of data in the destination.

ETL Testing Process

To explain the process of ETL Testing let us consider the example:

The multiple departments of an Organisation such as CRM, Inventory, Accounts, Sales, HR, and Loyalty. All these departments should have separate databases. If the company wants to analyze the data and generate reports on various activities it is needed to interconnect the databases properly. This process can complete successfully by using ETL tools.

The ETL testing process occurs just before the data is moved into a data warehouse system. The exact purpose of the ETL testing is to identify the extracted data defects and the errors that might occur prior to the processing of data.

Tasks in ETL Testing

  • Identify the exact data required for reporting.
  • Review the data model and mitigate the data structures.
  • Map from source to destination.
  • Data checks on the source data.
  • Detect the data defects after extracting data from the source databases.
  • Data Integrity and quality evaluation
  • Performance evaluation

ETL Process Diagram

The output of this collection of data can be used for OLAP [Online Analytical Processing ]Analysis, Reporting and Data Mining processes. The cubes provide multidimensional analysis of data collected from the data warehouses.

ETL Testing can be categorized

  • The New Data warehouse testing: The new data warehouse can be tested by taking the customer requirements as the input and can be analyzed from the scratch.
  • The Migration Testing: The migration of data from an existing data warehouse to another data warehouse should be tested for duplication of data.This testing can be effective to improve the efficiency
  • Source to Target Count Testing: Tests to ensure the count of the tables in source and destination remain same.
  • Source to target Data Validation: Tests to validate the data integration and threshold values in each record.
  • Data Mapping Testing: This testing process validates the mapping of the objects during the transformation.
  • End-user testing: This testing is to verify whether the data in the reports are as per the expectation.
  • System Integration Testing: This testing involves testing all the individual modules comparing the reports and checking for deviations in performance. Later combine the results of the performance evaluation.

Challenges in ETL Testing

  • Possibility of data loss
  • Occurrence of the duplicate data
  • Incompatibility of data while transferring
  • Complexity of huge data volume
  • Inefficiency in business processes
  • Difficulties in securing data

How to Perform the  ETL Testing

ETL testing can be processed either manually or by using some effective tools.Automated tools will be helpful to ensure that the data transferred to the destination are trustful. The testing methods like unit testing, functional testing, regression testing, integration testing, operations testing etc..are completed and evaluated by using tools.

The list of tools for ETL Testing are as given below:

  • Informatica MarketPlace
  • Querysurge
  • iCEQ
  • Datagaps ETL Validator

ETL Testing is a kind of enterprise testing as all the people like developers, business analysts, DB Administrators and end-users involved in it along with the test engineers. Also, it requires knowledge of  SDLC, SQL queries, and ETL Procedures. 

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