If you create MyModel.js and MyModel.json in loopback, but forget to add it to model-config.json, then will you see errors like:

Unhandled rejection TypeError: Cannot call method '<whatever>' of undefined?

Do you have to delete db.json to get past an error like the following?
Unhandled rejection TypeError: Object.keys called on non-object
at Function.keys (native)
at Memory.all (/node_modules/loopback-datasource-juggler/lib/connectors/memory.js:289:22)
at /node_modules/loopback-datasource-juggler/lib/dao.js:1210:38