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. Difficult data will be reported by __ tests if there are invalid characters, invalid character patterns, or wrong upper- or lowercase case. → Syntax
3. ___ automates ETL testing and management to make sure the data don't affect production systems. → Informatica Data Validation
4. Which test verifies that foreign key relationships in the target remain valid after an ETL load? → Referential integrity test
5. Which extraction type is MOST suitable when source systems do not support timestamps or change tracking? → Full extraction
6. What is 'pivoting' in the context of ETL transformation? → Converting rows to columns or columns to rows to reshape the data structure
7. 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
8. QualiDI's ___ testing platform provides ETL and end-to-end testing. → Automated
9. 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
10. When new data is introduced to existing data, a data integrity test is performed for ___ testing. → Incremental ETL
11. 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
12. Which transformation type converts a value from one unit to another, such as converting temperatures from Celsius to Fahrenheit? → Calculation/Derivation transformation
13. What ETL test checks that special characters (e.g., accents, Unicode) in source data are preserved after extraction? → Character encoding validation
14. An ETL job extracts data from multiple source systems. Which test type ensures that records from all sources are correctly merged in staging? → Multi-source integration test
15. What is an 'ETL batch window'? → The scheduled time period during which the ETL process must complete all data processing
16. In ETL testing, 'data completeness' during extraction specifically checks for: → All expected records and fields being present in the extracted dataset
17. ___ tests are run whenever data is transferred into production systems. → Production Validation
18. In ETL transformation testing, 'boundary value testing' for a transformation that caps sales amounts at $10,000 would test which values? → $9,999, $10,000, and $10,001
19. Which ETL validation approach computes an MD5 or SHA hash on source data and compares it to the same hash computed on target data? → Checksum validation
20. Which data extraction method is BEST for near-real-time ETL pipelines that need sub-minute latency? → Streaming CDC via Kafka or similar messaging
21. During ____, the main goal is to get data from a system as quickly as possible with the minimal trouble as possible for the system. → Extraction
22. Tests for ___ are generated automatically, saving time for test developers. → Application Upgrades
23. When testing a NULL-handling transformation rule that substitutes 0 for null numeric values, what test case is ESSENTIAL? → Send a record with a null numeric field and verify the target contains 0
24. Which ETL data quality dimension ensures that every required record and field is present in the target dataset? → Completeness
25. In the database, facts and aggregate facts are put into hierarchical groups called _____. → Dimensions
26. Which ETL performance test validates that parallel job streams do not cause database contention or deadlocks? → Concurrency / multi-user load test
27. The person conducting the performance and stress testing is _____. → Database Administrators
28. What ETL performance issue occurs when a single processing node becomes a bottleneck, slowing the entire pipeline? → Data skew
29. Which AWS service is commonly tested in US-based ETL pipelines to verify that Glue jobs correctly transform data? → AWS Glue job with PyTest and GlueContext mocking
30. Which extraction strategy is preferred when regulatory compliance requires zero impact on source system performance? → Offline extraction from a read replica or backup