Experiment Design. The subjects received a requirements document with the use cases and performed the creation of test cases with and without the tool support. After that, the subjects received another list to report the errors found during the test execution.
Arcade Games in Execution (from left to right: Brickles, Pong and Bownling respectively)
More details in: http://www.sei.cmu.edu/productlines/ppl/
Feature Model from Arcade Game
NotepadSPL in execution
More details in: http://featurevisu.sosy-lab.org/
Feature Model from NotepadSPL