White Box vs. Black Box testing

Black box and White box testing are mentioned a lot in Chapter 4 of the ISTBQ book.  The text book definition of black box in the ISTQB book states  that it is "testing either functional or non-functional, without reference to the internal structure of the component or system".  Basically Black box testing is when a tester knows what the software does from having access to things like requirements, but has no knowledge as to how the software does these things, or anything about the branching logic.  Black box testing tends to involve a lot of exploratory testing as the tester goes through the system to understand how the system works.  Techniques of black box testing include but are not limited to equivalence partitioning, and boundary value analysis, the use of data tables, and state transition testing


Meanwhile White box testing is defined as "Testing based on an analysis of the internal structure of the component or system".  In other words this type of testing is when the tester knows all the details about not only what the software supposed to do, but how it works and does what it's supposed to do.  These kinds of tests allow tester to increase their test coverage by finding new tests that haven't been created.  It uses techniques like statement coverage, decision coverage, and branch coverage.


Black box testing is good when the tester is starting to run tests on a software they know little about, while white box testing is good for going more in depth into understanding the system.