@kgatlast I don't think there is a definitive test for Long Covid. Here is more information from the CDC.

"There is no test that determines if your symptoms or condition is due to COVID-19. Long COVID is not one illness. Your healthcare provider considers a diagnosis of Long COVID based on your health history, including if you had a diagnosis of COVID-19 either by a positive test or by symptoms or exposure, as well as based on a health examination."
-- Long COVID or Post-COVID Conditions: https://www.cdc.gov/coronavirus/2019-ncov/long-term-effects/