The use of technology for teaching and learning has created a paradigm shifting in learning environments and learning process, and also the paradigm shifting has also affected the assessment processes. In addition to these, online environments provide more opportunities to assess of the learners. In this study, the Adaptive Mastery Testing (AMT) system in Assessment Management System was designed and developed in which students can test themselves, recognize their strengths and weaknesses, and determine their learning objective based competencies. AMT environment is structured in accordance with the rapid prototyping software developing model. In this environment, there are questions for the students about four learning objectives, which are among the basic subjects of the Statistics course. AMT environment consists of presentation, assessment, domain and learner model. Pilot implementation was carried out with 98 undergraduate students. In order to evaluate of the environment, number of tests taken, number of correct answer, number of wrong answer and number of total answer data were used. According to the findings, it is seen that most of the students are masters in the learning objectives presented to them. In addition, it was found that half of the students took an average test to become a master. In other words, half of the learners participating in the study were determined as masters by the system in the first test they took for each learning objective. [For the full proceedings, see ED621108.]