What is the test for granting a certificate of probable cause to appeal?

This court should grant an application for a certificate of probable cause to appeal only if the petitioner makes a substantial showing that he has been denied a federal right. Barefoot v. Estelle, 463 U.S. 880, 893, 103 S.Ct. 3383, 3394, 77 L.Ed.2d 1090 (1983). To make this substantial showing, a petitioner must demonstrate that the issues are "debatable among jurists of reason," that a court could resolve the issues differently, or that the issues are "adequate to deserve encouragement to proceed further." Id. at 893 n. 4, 103 S.Ct. at 3394 n. 4.