here is the CDC description of acceptable test:
"Passengers must be tested with a viral test that could be either an antigen test or a nucleic acid amplification test (NAAT). Examples of available NAATs for SARS-CoV-2 include but are not restricted to reverse transcription polymerase chain reaction (RT-PCR), reverse transcription loop-mediated isothermal amplification (RT-LAMP), transcription-mediated amplification (TMA), nicking enzyme amplification reaction (NEAR), and helicase-dependent amplification (HDA). The test used must be authorized for use by the relevant national authority for the detection of SARS-CoV-2 in the country where the test is administered. A viral test conducted for U.S. Department of Defense (DOD) personnel, including DOD contractors, dependents, and other U.S. government employees, and tested by a DOD laboratory located in a foreign country also meets the requirements of the Order."
The test I recently had took only 15 minutes total from filling out paperwork to receiving results. The swab is tested and the results show as a line or no line using what looks to be essentially a home pregnancy kit (one line good, two lines not good).