The current Covid-19 regulations for entry in to portugal include the presentation of a negative Covid test on entry. See a list of the EU approved Covid-19 test providers below.
There has been a lot of confusion as to which type of tests are now acceptable since the recent set of regulations was introduced. To clarify you must present a negative test from one of the manufacturers on this EU common approved list.
The type of test where you self test using a privately bought kit and upload a photo of your result to the company and receive your certificate to say you are negative is not acceptable, however there have been instances of these being accepted when previous regualtions were in place, and even since these current regulations were put in place.
To be sure, we suggest you use a test provider that is on the list.
You can find the list from page 10 of this document: https://ec.europa.eu/health/sites/default/files/preparedness_response/docs/covid-19_rat_common-list_en.pdf