Regression testing analyzes whether software
maintenance has inadvertently broken existing functionality.
Since it is costly—especially for manual testing—it is typically
limited to a subset of test cases. Since impact analysis of code
modifications on test cases is far from trivial for real world
software, regression test selection is hard. However, if it misses
affected test cases, bugs may remain unnoticed. In response,
the research community has proposed numerous test selection
approaches. Regression test selection is especially relevant for
manual tests, since their execution costs limit the number of
tests that can be executed in practice. However, evaluations
of existing work focus on automated tests. Its applicability to
manual tests is thus unclear. We present an industrial case
study that demonstrates the challenges that regression test
selection techniques face when applied to manual system tests.
Furthermore, we sketch how, given these challenges, manual
regression test selection can be improved.