First, nvm install && npm ci. Then,

1) Observe source map support

Without changes, npm test yields the following (excerpt):

  1) #makeSandwich
       does not throw:
     Error: no ingredients
      at makeSandwich (a.js:2:9)
      at Context.<anonymous> (test.js:5:5)
      at processImmediate (internal/timers.js:439:21)

2) Enable rollup-plugin-stub

Uncomment the plugin inclusion in rollup.plugin.js. Then rerun npm test. One finds:

  1) #makeSandwich
       does not throw:
     Error: no ingredients
      at makeSandwich (dist/bundle.js:2:9)
      at Context.<anonymous> (dist/bundle.js:7:5)
      at processImmediate (internal/timers.js:439:21)