Component Test Case provides a visual test case builder for defining the data sources and validations. Some of the common scenarios where the Component Test Case can be used are listed below : 

• Compare data in a Flat File with the Database Query
• Compare data from Multiple Sources to Target
• Incremental data load testing
• Regression testing of the ETL by baselining and comparing data in Target tables
• Testing complex transformations

This video explains how to compare data from multiple sources with the target : 

Flat files are commonly used in the enterprise to exchange data between organizations or from external sources. Testing of quality of the Flat file and the comparing it with data in the target database or another flat file is another scenario where the Component Test Case can be used