The U.S. Constitution Test (which satisfies the U.S. Constitution requirement for the California Teaching Credential Program) is no longer being offered through the Tutoring, Learning, and Testing Center at Chapman University.
Some other schools that offer this exam include:
CSU Dominguez Hills (through the Political Science Department) - http://www4.csudh.edu/political-science/constitution-exam/index
UCLA (through UCLA Extension and the Department of Education) - https://www.uclaextension.edu/
Please contact them well in advance for testing availability.