The greatest lower bound to the reliability of a test, based on a single administration, is the Greatest Lower Bound (GLB). However the estimate is seriously biased. An algorithm is described that corrects this bias.
Bendermacher, N. (2017). An unbiased estimator of the greatest lower bound. Journal of Modern Applied Statistical Methods, 16(1), 674-688. doi: 10.22237/jmasm/1493598960