What is ERA testing? Endometrial receptivity array (ERA) is a diagnostic procedure that may help determine whether the endometrial cavity is ready for embryo implantation. ERA involves biopsying a small sample of the endometrium, or lining of the uterus, for molecular analysis. Fertility expert Mr. Evripidis Mantoudis FRCOG comments: According to new data it appears that ERA test does not predict the implantation window. Although it had been promoted at conferences in recent years, I had always been skeptical about its value and whether it could deliver what it promised.