A life distribution F with survival function F=1-F, finite mean μ and mean residual life e(t) is said to be NBUE (NWUE) if e(t)⩽(⩾)μ for t⩾0. This NBUE (NWUE) property can equivalently be characterized by the fact that φ(u)⩽(⩾)u for 0⩽u⩽1, where φ(u) is the scaled TTT-transform of F. A generalization of the NBUE and NWUE properties is that there is a value of s such that φ(u)⩾u for 0⩽u⩽p and φ(u)⩽u for p⩽u⩽1, or vice versa. This means a trend change in the NBUE property. This generalized aging property is called the NBUE-NWUE property. In this paper the authors present and study a test statistic intended for testing exponentiality (i.e. φ(u)=u for 0⩽u⩽1) against this NBUE-NWUE property. The asymptotic normality of the test statistic, suitably normalized, is established and a simulation study is presented (20 refs.)