These guidelines were first published July 14, 2020, and are periodically updated: https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/COVID-19/Updated-COVID-19-Testing-Guidance.aspx
The California Department of Consumer Affairs created a flyer showing these guidelines. You can download the flyer here: https://www.dca.ca.gov/licensees/covid19_testing_priority.pdf