So, `ngrok` is a program that tries to keep open a connection to a remote server, reconnecting as needed. `wget`'s test confirms that grabbing google.com's index completes as expected (and fails when there's no network connection of course). `ngrok` never 'completes'...

One thing we could do is something like `Open3.popen3("#{bin}/ngrok -log stdout 8080") do |stdin, stdout, _|`... and in the block check that the first line of stdout is doing something we expect (in this case, reading the config file). https://github.com/Homebrew/homebrew/blob/master/Library/Contributions/example-formula.rb gave me this idea.

Is there a better way to 'test' ngrok is correctly installed? @inconshreveable - thoughts?