In many cases now, countries are asking for a negative COVID test prior to your flight back. Here you have some information about where can you get these test in Valencia:

UNIVERSIDAD CATÓLICA DE VALENCIA. Antigen test costs 20€ and results and certificate are given within 15 minutes. You have to book it in advance and pay through the web page https://www.ucv.es/clinicas-ucv/pruebas-diagnosticas-covid-19. Click on the on-line appointment (https://www.ucv.es/prueba-citas/clinicas.aspx) and you will see an area with flags to select the language and the right treatment (test) and follow the instructions. Opening hours from 9:00 to 19:40.

It is located in the city center right next to the central market (Plaça de la Ciutat de Bruges, 6, 46001 València, Valencia)

VALENCIA AIRPORT. https://eurofins-megalab.com/en/eurofins-megalab-is-carrying-out-testing-for-covid-in-12-spanish-airports/. This costs about 40 euros, however if you are flying with some companies like Iberia you can find vouchers (see the tab vouchers in the same webpage) and the cost is reduced to around 30 euros. Opening hours from 8:00 to 17:00.

CASA SALUD HOSPITAL. (https://lasaludhospital.es/pruebas-covid-valencia) Located close (25 min walk) to the UPV. Be aware that the testing area is not in the Hospital complex but in a building next to it (Calle Salvador Pau, 37, 46021 València, Valencia). Opening hours from 8:00 to 19:00 Monday to Friday and 8:00 to 14:00 Saturday and Sunday. No booking in advance. Antigen test 40 euro.

QUIRON HOSPITAL. You can book it in advance (https://e-quironsalud.es/test-covid/82-test-antigeno-rapido) Select Valencia and Hospital Quiron Valencia. Opening hours from 8:00 to 14:00 Monday to Friday and 8:00 to 12:00 Saturday and Closed on Sunday. Cost:40 euros.