  We study the problem of mismatched likelihood ratio test. We analyze the
type-\RNum{1} and \RNum{2} error exponents when the actual distributions
generating the observation are different from the distributions used in the
test. We derive the worst-case error exponents when the actual distributions
generating the data are within a relative entropy ball of the test
distributions. In addition, we study the sensitivity of the test for small
relative entropy balls.
