ETL Testing MCQ 4

Question 1

In ETL testing, what does 'data completeness' testing verify?

Accepted Answer

That all expected records and fields are present in the target without omission

Answer

Data completeness testing ensures every record from the source appears in the target and that no columns, rows, or values are missing after the pipeline runs.

Question 2

Which type of ETL bug would cause a sales amount to be loaded as 1000 instead of the correct 10.00?

Accepted Answer

Decimal precision or scaling error

Answer

A decimal precision error—such as omitting a scale factor or mishandling decimal points—can shift values by orders of magnitude during transformation.

Question 3

What is the role of a 'surrogate key' in a data warehouse target table, and what ETL test validates it?

Accepted Answer

It replaces business keys; tested by verifying no NULLs and uniqueness

Answer

Surrogate keys are system-generated unique identifiers replacing natural business keys; ETL tests confirm they are non-null, unique, and properly assigned to every loaded row.

Question 4

An ETL process aggregates daily sales into monthly totals. Which test would catch an off-by-one error in the aggregation date range?

Accepted Answer

Boundary date range test

Answer

Boundary date range tests use records on month start/end dates (e.g., Jan 31 vs Feb 1) to confirm the aggregation window includes or excludes the correct days.

Question 5

What does 'CDC' stand for in the context of ETL pipelines, and what is its purpose?

Accepted Answer

Change Data Capture — tracks and extracts only changed source records

Answer

Change Data Capture monitors source system logs or timestamps to identify and extract only the records that have been inserted, updated, or deleted since the last run.

ETL Testing - extract, transform, load Practice Test

ETL Testing - extract, transform, load Practice Test

ETL Testing MCQ 4