"yarn test" coughs a hard error

[MikeTheCanuck]

While adding my first additional unit test, I tried to verify that yarn test would work in my local environment and show this next test working.

Instead, it coughed hard - and even without the new test:

$ yarn test
yarn run v1.3.2
$ react-scripts test --env=jsdom
2017-12-05 12:42 node[28987] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
2017-12-05 12:42 node[28987] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
2017-12-05 12:42 node[28987] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
events.js:183
      throw er; // Unhandled 'error' event
      ^

Error: Error watching file for changes: EMFILE
    at _errnoException (util.js:1024:11)
    at FSEvent.FSWatcher._handle.onchange (fs.js:1351:9)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
Mikes-MacBook-Pro15:WhoDidITalkTo mike$ yarn test
yarn run v1.3.2
$ react-scripts test --env=jsdom
2017-12-05 12:43 node[29017] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
2017-12-05 12:43 node[29017] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
2017-12-05 12:43 node[29017] (FSEvents.framework) FSEventStreamStart: register_with_server: ERROR: f2d_register_rpc() => (null) (-22)
events.js:183
      throw er; // Unhandled 'error' event
      ^

Error: Error watching file for changes: EMFILE
    at _errnoException (util.js:1024:11)
    at FSEvent.FSWatcher._handle.onchange (fs.js:1351:9)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[MikeTheCanuck]

And apparently this is one solution that has worked for some (installing watchman tool):
facebook/create-react-app#871

In fact, that guidance has migrated to the React Scripts README, though it's implied rather than called out directly.

Once I ran brew install watchman, the next execution of yarn test worked like a charm.