Two tests were developed to determine the students’ understanding level of selected fundamental electrochemistry concepts namely: the cathode, anode, minus, plus, electrolysis, galvanic cell, and transport of charges in electrolyte solution. One of the tests included 15 open-ended questions developed from the studies of Sanger and Greenbowe (1997b). The validity of the test was provided by the researchers and the experts. For this purpose, two chemistry educators, one science educator, three chemists and five chemistry teachers were consulted. This test is called "Electrochemistry Open-ended Test (OET)". The other test consisted of 11 multiple choice questions. The data obtained from the questions were developed by the researcher who used the study published by Schmidt, Marohn, and Harrison (2007). The validity of the test was provided by the examination of two chemistry educators, one science educator, three chemists and five chemistry teachers. The reliability of the Electrochemistry Multiple Choice Test (MCT) based on KR-21 was 0.78. There are two conditions for KR-21 reliability. The first one is the grading of test 1-0. The second one is the usage of KR-21 when the item difficulty index is unknown. KR-21 is calculated based on the arithmetical average of the test.