ETL Testing MCQ 5

Question 1

What is 'schema drift' in ETL testing, and why is it a concern?

Accepted Answer

When source schema changes (added/removed columns) break the ETL pipeline unexpectedly

Answer

Schema drift occurs when source systems silently alter their structure, causing ETL jobs to fail or load incorrect data because the pipeline was built against an older schema.

Question 2

A lookup transformation in an ETL returns the wrong country code for 2% of records. What is the FIRST step a tester should take?

Accepted Answer

Isolate the affected records and compare lookup table values against source expectations

Answer

Isolating the 2% of mismatched records and comparing them against the lookup reference table reveals whether the issue is stale lookup data, missing entries, or a transformation bug.

Question 3

Which ETL testing phase checks that the data warehouse meets query performance SLAs after a full data load?

Accepted Answer

Performance and load testing

Answer

Performance and load testing measures query response times, ETL throughput, and resource utilization after loading realistic data volumes to validate SLA compliance.

Question 4

What does testing for 'data consistency' across multiple subject areas in a data warehouse mean?

Accepted Answer

Verifying that shared dimensions and metrics report identical values across fact tables

Answer

Data consistency testing confirms that a dimension like 'Customer' or a metric like 'Revenue' returns the same result whether queried from the Sales or Finance fact table.

Question 5

In an ETL pipeline that loads data from a flat file, which test specifically catches issues with incorrect delimiter handling?

Accepted Answer

File format and delimiter parsing test

Answer

File format and delimiter parsing tests verify that the parser correctly splits columns using the expected delimiter, catching cases where commas in data values break CSV parsing.

ETL Testing - extract, transform, load Practice Test

ETL Testing - extract, transform, load Practice Test

ETL Testing MCQ 5