A model for the s-expected cost of a development testing program is presented in this paper. The total cost function consists of two terms. The first term is proportional to the duration of the testing program; the second term is a loss function that assesses additional costs for failure to meet reliability goals during the testing program. The reliability growth model assumes that failures during the program occur according to a nonhomogeneous Poisson process having a power-law rate. An example shows how the duration of the test program can be chosen to minimize s-expected total cost.