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When concerning about data warehousing, it is required to have some kind
of a knowledge to test them. Today I'll share with you some details
about data warehousing.

Simplest definition
A data warehouse is the data (meta/fact/dimension/aggregation) and the
process managers (load/warehouse/query) that make information available,
enabling people to make informed decisions.

What areas to be tested on a data warehouse
1. Sufficient testing needs to be performed to establish that queries
scale with the data.
2. Full-scale testing requires a comprehensive test plan
3. If the test data is generated, ensure the data has the correct
balance and skew. Make sure the ratio of fact to dimension is correct
and so on.
4. Every backup test should be verified by performing recovery using the
backedup data.
5. Take the time to test the most complex and awkward queries that the
business is likely to ask against different index and aggregation
strategies.

There are some more areas to be concerned than this. This may help you
to get an idea about data warehouse.

Ref: Data Ware housing in the real world by Sam anahory and Dennis
Murray.