Assessing students higher-order thinking skills is still challenging for mathematics teachers in Indonesia. This paper aims to develop a test that is valid, reliable, practical, and effective to assess students’ higher-order thinking skills in mathematics learning. The Plomps’ developmental model, Generic model for Educational Design, was deployed to develop the test. The method consisted of 4 phases; (1) Problem analysis, (2) Design, (3) Develop, and (4) Evaluation and Implementation. The quality of the developed test was examined by using Plomps’ product quality criteria; (1) Validity, (2) Reliability, (3) Practicality/usability, and (4) Effectiveness. The test was validated by 2 validators that are experts on HOTS in mathematics and trial. Meanwhile, the practicality/usability of the test was examined by 5 mathematics teachers from different Junior High schools. The Effectiveness was measured by trial on 3 primary schools. The validity and reliability were measured using the Expert Agreement Index (EAI) from Gregory. The rubric's practicality was analyzed using practicality product criteria and the effectivity of the test was analyzed by using a two-tailed t-test. The research shows that the validity of the test is 0.88 (high validity) and the reliability is 0.93 (reliable). The practicality of the test is 75.26 (Practical). The trial on the lower-index, middle-index and higher-index schools found that the higher-order thinking skill is effective to implement. In conclusion, the HOTS test is valid, reliable, practical, and effective to use to measured students’ higher-order thinking skills in mathematics learning.