This legislation, titled the "Diagnostics Testing Preparedness Plan Act of 2025," amends the Public Health Service Act to mandate the Secretary of Health and Human Services (HHS) to develop, publicly release, and regularly update a comprehensive plan. This plan is designed to improve the rapid development, validation, authorization, manufacture, procurement, and distribution of diagnostic tests, as well as the scaling of testing capacity, in response to public health emergencies stemming from chemical, biological, radiological, or nuclear threats, including emerging infectious diseases. The plan's primary purposes are to facilitate the development and utilization of diagnostic tests, describe efficient processes for their deployment, and foster coordination and collaboration among public and private entities. Key considerations for the plan include assessing domestic capacity , integrating novel technologies like high-throughput, point-of-care, and rapid at-home diagnostics, addressing medical supply chain vulnerabilities, and establishing strategies for efficient test distribution. The Secretary is required to coordinate with industry, states, local governments, and tribal organizations, and may contract with public and private entities to build domestic capacity. The initial plan must be publicly released within one year of enactment and updated at least every three years thereafter.