With older versions of angular-cli, you used to be able to use both --singleRun and --watch=false for the same thing. Now they removed --singleRun.
You can still use ng test --watch=false
Angular cli 1.x docs
Tests will execute after a build is executed via Karma, and it will automatically watch your files for changes. You can run tests a single time via –watch=false or –single-run.
Angular cli 6.x docs
Tests will execute after a build is executed via Karma, and it will automatically watch your files for changes. You can run tests a single time via –watch=false.