A cognitive diagnostic test is required in learning activities to diagnose the ability and
students‟ weaknesses through the stage of thinking. With diagnostic test is expected to the
aim of learning that have not been known by the students can be identified and known the
problems. The purpose of this study is to develop a diagnostic test of cognitive science and to
obtain characteristics of cognitive diagnostic test in science subjects. The research used the
development of diagnostic tests. The trials conducted in seven schools that have with high
category, medium and low school category. Test subjects of the seventh grade students were
484. Development of data analysis based on descriptive cognitive diagnostic test done
through Focus Group Discussion (FGD). Selection of test items is to obtain fit tests using the
Quest program. Through FGD produces Learning Continuum, grating test, test specifications
and item 28 in the form of multiple choices with reasons. By using the Quest program
obtained 27 items fit is to see that the items are in a vertical line or have infit MNSQ between
0.77 until 1.30. Instrument reliability value is 0.74. The research instrument is compliant with
the statistical Fit with an average value of infit MNSQ 1.01 with a standard deviation 0.09.