ETL Testing: How to Assess Performance

Hacker analyzing softwareETL systems are for the integration of data from multiple sources. In a world of businesses run by digitalized data, these software systems are vital to ensure the continued performance of your company and its data. Udemy offers many class than can help you not only learn the basics of data warehousing, the umbrella under which ETL systems reside, but also the basics of mastering ETL systems. Learn how to test your ETL systems to ensure they work efficiently and smoothly.

What is ETL?

ETL stands for “Extract, Transform, Load.” In the digital, computing world, this is a process for databases and their usage in regard to their data warehousing. The primary functions are as follows:

  • Extracting data from outside sources;
  • Transforming data to fit a business’s operational needs, including quality levels of the data.
  • Loading data into the target, which usually is a database, more specifically known as data warehouse, operational data store, or data mart.

Thus, ETL systems merge data from multiple sources, validate that the data meets a company’s specific needs and changes the data if it does not, and loads it into their data warehouse.

The most challenging step of this process is the first, that of data extraction. If this step does succeed, then the sequential proceeding steps will fail as well since there will be no data to work with. For more information on this vital step, Udemy offers a thorough course on different data extraction tips and tricks.

The next step, the transformation of the extracted data, occurs whenever the data is applied to a set of given rules or functions to obtain the required data, and removing the unnecessary information. Sometimes this is either a simple process as there is little to no change required for the data, or it is long and complicated depending on the business’s technical, format needs.

The loading is the final step in this process where the extracted data, now transformed, is loaded into an end target, usually a data warehouse. Depending on the needs of a company, this too is either a simple or complicated process. Sometimes data warehouses are required to overwrite existing information. This is subject to how often data is extracted and loaded, whether it on a hourly, daily, monthly, or yearly basis. Over time, the warehouse will delete old information for the new to take its place.

This could be problematic for those businesses that need to keep viable records for longer periods of time; however, with the proper knowledge of how to manage a database, something you can learn about on Udemy and data analysis, one could easily navigate the digital systems of data warehouses and the audit trails of their history.

Why Test ETL Systems?

Of course, if these software systems are in place and usually work by themselves with little to no supervision, why is there a need to test them? The answer is simple – to keep them functioning with as few errors as possible on a regular basis. As ETL systems are used for the consolidation of a company’s data and the information it needs to work efficiently, if the ETL system is flawed your data will be flawed as well.

There are different types of ETL testing, each for a different purpose. These include:

  • New Data Warehouse Testing: This is the construction of a new warehouse for your data.
  • Migration Testing: This uses your existing data warehouse and ETL system to look for new tools to help improve the performance of your system.
  • Change Request: This adds new data to existing data warehouses, and changes different business policies in regard to data requirements.
  • Report Testing: Tests the end results of data warehouses by validating the layout, data, and calculation.

These different types of ETL tests will help verify the function of your system and its warehouse.

The ETL Testing Process

The process of testing your ETL system is similar to most other verification programs within your business. As such, some of the phases are shared between different processes.

As always, you must begin with a mutual understanding of your business requirements as this outlines the functions for any work done within the company. Second, give yourself a reasonable estimate of how much this test will cost your company. This is more about time, availability of resources, and possible complications more than money. As testing requires a certain amount of downtime for your computing systems, but sure to realistically give your company an estimate of how long this will take.

Next, plan out the testing process and results, and remember how you need it to fit your inputs of test estimates and business requirements. Leave nothing out, as this is the forecast for the actual testing period, and doing so will only cause further complications during the testing. Make sure to also design different cases and scenarios that will occur within the allotted testing time based on your inputs.

After all the preliminary planning, you are ready to begin you testing, but only after your chosen team has performed pre-execution checks and has prepared the data for testing. The execution is then performed until the exit criteria has been met, and everything is finished when the summary report is written and the closure process has concluded.

Different ETL Testing Techniques

There are also different techniques to remember that will help the testing of your ETL systems.

  • Always verify your data. If data is not being transformed according to your business rules, then chances are something is wrong. If it is your business rules, then perhaps there is no mutual understanding between parties that should be carefully reexamined.
  • Check that all projected data is sufficiently loaded within the data warehouse. This will cut down on needing to search for missing or lost data.
  • Make sure your ETL application is appropriately rejecting default values and invalid data and replacing it.
  • Finally, be sure that your data is being loaded into the data warehouse within the allocated time frame set up by your company. This ensures your systems are functioning not only properly, but in a timely manner.

While there are other testing methods, these four are the more common of any unmentioned technique you could test your ETL system.

Regular testing of your ETL system will help keep your company’s data warehouses clear of clutter-like data, and inevitably help the functioning of your business. Check out Udemy’s course on Mastering the Basics of ETL Systems for more information – this is one of the best ways you have to ensure your company’s future as its data is protected.