ETL TESTING Cheat Sheet 2026

The 30 highest-yield ETL TESTING facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. In ETL scalability testing, 'horizontal scaling' refers to: → Adding more processing nodes or worker instances to distribute the ETL workload
2. Which ETL testing type checks that business rules encoded in transformations produce the correct output values? → Transformation testing
3. Which strategy is most appropriate for testing an ETL pipeline's behavior under maximum expected data volume? → Volume or stress testing using a dataset sized to production scale or beyond
4. Which testing technique involves re-running the full ETL process with the same source data to confirm results are identical? → Idempotency testing
5. Which ETL testing phase checks that the data warehouse meets query performance SLAs after a full data load? → Performance and load testing
6. In an ETL pipeline that loads data from a flat file, which test specifically catches issues with incorrect delimiter handling? → File format and delimiter parsing test
7. Which error-handling strategy continues processing remaining records after encountering a bad row, rather than aborting the entire job? → Skip-and-log strategy
8. Difficult data will be reported by __ tests if there are invalid characters, invalid character patterns, or wrong upper- or lowercase case. → Syntax
9. ___ automates ETL testing and management to make sure the data don't affect production systems. → Informatica Data Validation
10. When testing ETL, what does 'data lineage' refer to? → The traceable path data follows from source through transformations to target
11. Which test verifies that foreign key relationships in the target remain valid after an ETL load? → Referential integrity test
12. Which extraction type is MOST suitable when source systems do not support timestamps or change tracking? → Full extraction
13. A transformation converts a date from MM/DD/YYYY to YYYY-MM-DD format. Which test type directly validates this rule? → Transformation / mapping validation testing
14. What is 'delta extraction' in ETL? → Extracting only records that have changed since the last ETL run
15. What is 'pivoting' in the context of ETL transformation? → Converting rows to columns or columns to rows to reshape the data structure
16. In an ETL pipeline, a surrogate key is typically validated to ensure which of the following properties? → It is unique and not NULL for every row in the dimension table
17. QualiDI's ___ testing platform provides ETL and end-to-end testing. → Automated
18. A trigger-based extraction fires a database trigger on DML events. What is a key risk of this approach? → It adds performance overhead to the source system
19. Which ETL testing technique compares row counts between the source and target to detect data loss? → Reconciliation testing
20. What is 'schema drift' in ETL testing, and why is it a concern? → When source schema changes (added/removed columns) break the ETL pipeline unexpectedly
21. Which ETL testing approach validates that transformations applied to personally identifiable information (PII) comply with data masking requirements? → Data security and masking validation testing
22. When new data is introduced to existing data, a data integrity test is performed for ___ testing. → Incremental ETL
23. What does testing for 'data consistency' across multiple subject areas in a data warehouse mean? → Verifying that shared dimensions and metrics report identical values across fact tables
24. Which approach best prevents duplicate records when running incremental ETL loads? → Using a high-watermark or last-run timestamp combined with an UPSERT (merge) operation
25. Which test approach verifies that an ETL transformation produces the correct output for ALL documented business rules simultaneously on a sample dataset? → End-to-end transformation regression test
26. Which ETL testing scenario best tests the 'reject' or 'error' handling logic of a pipeline? → Injecting records that violate business rules or constraints
27. Which transformation type converts a value from one unit to another, such as converting temperatures from Celsius to Fahrenheit? → Calculation/Derivation transformation
28. What does the acronym 'ETL' stand for in data warehousing? → Extract, Transform, Load
29. What ETL test checks that special characters (e.g., accents, Unicode) in source data are preserved after extraction? → Character encoding validation
30. Which tool category is MOST commonly used for automated ETL regression testing? → Data comparison tools like QuerySurge or Informatica Data Validation