Testing Billing API Issue

Hi,
when i run the mock test to validate the billing-event,
#serverless invoke local --function billing --path mocks/billing-event.json

i get this:

Serverless: DOTENV: Loading environment variables from .env:
Serverless: 	 - STRIPE_SECRET_KEY

  Type Error ---------------------------------------------

  TypeError [ERR_INVALID_ARG_TYPE]: The "to" argument must be of type string. Received type undefined
      at validateString (internal/validators.js:107:11)
      at Object.relative (path.js:1052:5)
      at /training-dir/notes-app-api/node_modules/serverless-webpack/lib/validate.js:186:36
      at arrayMap (/training-dir/notes-app-api/node_modules/lodash/lodash.js:639:23)
      at Function.map (/training-dir/notes-app-api/node_modules/lodash/lodash.js:9554:14)
      at processConfig (/training-dir/notes-app-api/node_modules/serverless-webpack/lib/validate.js:183:37)
      at ServerlessPlugin.validate (/training-dir/notes-app-api/node_modules/serverless-webpack/lib/validate.js:232:14)
      at ServerlessPlugin.tryCatcher (/training-dir/notes-app-api/node_modules/bluebird/js/release/util.js:16:23)
      at Promise._settlePromiseFromHandler (/training-dir/notes-app-api/node_modules/bluebird/js/release/promise.js:547:31)
      at Promise._settlePromise (/training-dir/notes-app-api/node_modules/bluebird/js/release/promise.js:604:18)
      at Promise._settlePromiseCtx (/training-dir/notes-app-api/node_modules/bluebird/js/release/promise.js:641:10)
      at _drainQueueStep (/training-dir/notes-app-api/node_modules/bluebird/js/release/async.js:97:12)
      at _drainQueue (/training-dir/notes-app-api/node_modules/bluebird/js/release/async.js:86:9)
      at Async._drainQueues (/training-dir/notes-app-api/node_modules/bluebird/js/release/async.js:102:5)
      at Immediate.Async.drainQueues [as _onImmediate] (/training-dir/notes-app-api/node_modules/bluebird/js/release/async.js:15:14)
      at processImmediate (internal/timers.js:439:21)
      at process.topLevelDomainCallback (domain.js:126:23)

     For debugging logs, run again after setting the "SLS_DEBUG=*" environment variable.

  Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues
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  Your Environment Information ---------------------------
     Operating System:          darwin
     Node Version:                 14.2.0
     Framework Version:        1.70.0
     Plugin Version:                3.6.11
     SDK Version:                   2.3.0
     Components Version:      2.30.10

I am stuck at this point and any help will be appreciated to get the expected output per the Text

It’s really hard to know whats going on based on that. It seems like it might be a config related issue. You can try prefixing your command with SLS_DEBUG=* to get more debug info.