  We have recently witnessed tremendous success of Machine Learning (ML) in
practical applications. Computer vision, speech recognition and language
translation have all seen a near human level performance. We expect, in the
near future, most business applications will have some form of ML. However,
testing such applications is extremely challenging and would be very expensive
if we follow today's methodologies. In this work, we present an articulation of
the challenges in testing ML based applications. We then present our solution
approach, based on the concept of Metamorphic Testing, which aims to identify
implementation bugs in ML based image classifiers. We have developed
metamorphic relations for an application based on Support Vector Machine and a
Deep Learning based application. Empirical validation showed that our approach
was able to catch 71% of the implementation bugs in the ML applications.
