Coronavirus: Brazil overtakes Spain and Italy as new cases grow
bbc.com
bbc.com
Otherwise a country that does close to no testing might have the illusion of doing very well, just like a country doing tons of tests might have the illusion of doing very poorly (like the US, whose ratio of positive has been declining for 1.5 months but number of cases is rather flat due to ever increasing testing)
For starters, every country has their own definitions and testing strategies. Then an overwhelming majority of cases are asymptomatic and almost never show up in official numbers.