That ranking's not terribly informative. A lot of the countries heading it up are smaller ones since most countries are drawing from the same global pool of testing consumables, meaning that there's not much relationship between the difficulty of carrying out a particular number of tests and the size of the country, it's total tests done which doesn't tell you much about current testing rate, and large developed Western countries are close enough in testing rates that an actual ranking based on them probably wouldn't be very stable anyway.