  This paper proposes a novel column generation framework for combinatorial
software testing. In particular, it combines Mathematical Programming and
Constraint Programming in a hybrid decomposition to generate covering arrays.
The approach allows generating parameterized test cases with coverage
guarantees between parameter interactions of a given application. Compared to
exhaustive testing, combinatorial test case generation reduces the number of
tests to run significantly. Our column generation algorithm is generic and can
accommodate mixed coverage arrays over heterogeneous alphabets. The algorithm
is realized in practice as a cloud service and recognized as one of the five
winners of the company-wide cloud application challenge at Oracle. The service
is currently helping software developers from a range of different product
teams in their testing efforts while exposing declarative constraint models and
hybrid optimization techniques to a broader audience.
