Definition: A data warehouse is a central store of data brought together from multiple source systems, organised to support reporting, analysis and decision-making. Data is usually transformed and structured on the way in, often into fact tables and dimensions.
So what? Business decisions often rest on what a data warehouse reports. Testing it means checking that data from each source arrives complete and correct, and that combining sources doesn't distort the picture.
Examples: A mortgage provider combining customer, payment and arrears data to produce management information. A team bringing in a new data source and checking how it aligns with existing customer data.
