Breadth Testing is a test suite that validates the full functionality of a product but does not test the product features in detail.
Let us also understand Breadth testing from integration testing point of view.
Top-down integration testing can either take depth-first or a breadth-first approach. In breadth-first testing, all the modules are refined at the same level of control. In reality, a combination of the both breadth-first testing and depth-first testing approach is used.
At the early stages of development, all the modules might be developed only partially. These modules are tested in breadth-first manner, and over a period of time all these modules would be delivered with successive refinements, which would be close to the full functionality of the product. Hence, depth-first testing of a module ought to be performed simultaneously with breadth-first testing.