Consider the Neyman-Pearson lemma. For testing $H_0: \theta=\theta_0$ vs $H_1: \theta=\theta_1$, if the likelihood ratio $\Lambda(x) = \frac{L(\theta_0|x)}{L(\theta_1|x)}$ is used to define the rejection region $R = \{x : \Lambda(x) < k\}$, what is the property of this test?