This document discusses assessing student learning outcomes in one-shot library sessions. It introduces the assessment cycle of defining student learning outcomes, developing assessments, implementing assessments, assessing achievement, and using results for improvement. Several classroom assessment techniques are described, such as one-sentence summaries and defining features matrices, that can be used to evaluate whether students are learning and which content is being learned. The document provides tips for setting benchmarks to measure the percentage of students successfully achieving learning outcomes and outlines collecting and analyzing assessment data to make data-driven decisions for improving future sessions.