Is there a way to testfor a collective scoreboard?
Solution 1:
You can use /scoreboard players operation to add all scores up and put them into one score. These two commands put the sum of all scores in the scoreboard "hello" into the score "sum" for the real or imaginary player "Horst":
/scoreboard players set Horst sum 0
/scoreboard players operation Horst sum += * hello
Scoreboard "sum" has to exist already, but Horst doesn't. This iterates one every entry in the scoreboard "hello" and adds its value to Horst's score, which is initially 0. You can also replace * with a target selector.