Imagine some program and a number of changes. If none of these
changes is applied (“yesterday”), the program works. If all changes are applied
(“today”), the program does not work. Which change is responsible for the failure?
We present an efficient algorithm that determines the minimal set of failure inducing
changes. Our delta debugging prototype tracked down a single failure inducing
change from 178,000 changed GDB lines within a few hours.

The analysis uses roles as the basis for three abstractions:
role transition diagrams, which present the observed transitions
between roles and the methods responsible for the
transitions; role relationship diagrams, which present the observed
referencing relationships between objects playing different
roles; and enhanced method interfaces, which present
the observed roles of method parameters.

Together, these abstractions provide useful information
about important object and data structure properties and
how the actions of the program affect these properties. We
have used our implemented role analysis to explore the behavior
of several Java programs. Our experience indicates
that, when combined with a powerful graphical user interface,
roles are a useful abstraction for helping developers
explore and understand the behavior of object-oriented programs.