Add '--no-watch' flag for tests (#6285)

Author: ricokahler

packages/react-scripts/scripts/test.js

@@ -54,17 +54,24 @@ function isInMercurialRepository() {
   }
 }
 
-// Watch unless on CI, in coverage mode, or explicitly running all tests
+// Watch unless on CI, in coverage mode, explicitly adding `--no-watch`,
+// or explicitly running all tests
 if (
   !process.env.CI &&
   argv.indexOf('--coverage') === -1 &&
+  argv.indexOf('--no-watch') === -1 &&
   argv.indexOf('--watchAll') === -1
 ) {
   // https://github.com/facebook/create-react-app/issues/5210
   const hasSourceControl = isInGitRepository() || isInMercurialRepository();
   argv.push(hasSourceControl ? '--watch' : '--watchAll');
 }
 
+// Jest doesn't have this option so we'll remove it
+if (argv.indexOf('--no-watch') !== -1) {
+  argv = argv.filter(arg => arg !== '--no-watch');
+}
+
 // @remove-on-eject-begin
 // This is not necessary after eject because we embed config into package.json.
 const createJestConfig = require('./utils/createJestConfig');