Here's the full quote from the WHO Director-General.
The very next sentence makes clear "test, test, test" refers to suspected cases.
It does not mean test asymptomatic people. Indeed the WHO makes this explicitly clear.
What an absolute disaster. The UK is now an international disgrace, a rogue state and completely out on a limb.... it’s heartbreaking really but totally avoidable. Scotland needs Independence from this mess! https://twitter.com/bbcpolitics/status/1311596681612460033
First Minister @NicolaSturgeon: "The total number of positive cases that were reported yesterday is 668. That is 10.8% of people newly tested yesterday. That takes the total number of cases now to 29,912."