This research work will give you an overview of the topics covered on the development of assessments, Proficiency Testing and theories of measurement. In addition, it will provide you with full description of proficiency test construction, test alignment with curriculum based on skills, items selection criteria for proficiency tests, minimum number of items required for assessing each skill/content area, sample questions, test calibration procedure, test interpretation, development of students performance levels and testing tips that may assist you in preparing proficiency assessments. It also explores the meaning of content and performance standards, development of academic and assessment standards, and benchmarks and indicators. It will also guide you to use of item response theory IRT and classical test theory CTT in standardized test development. Discussion on test reliability and validity in terms of IRT and CTT is special theme of this research work.