Jest - TypeError: Cannot read property 'fn' of undefined

Out of nowhere, I'm having an issue when running certain Jest tests: Summary of all failing tests FAIL server/controllers/voice/settings/tests/voice.settings.controller.test.js ● Test suite failed to run

TypeError: Cannot read property 'fn' of undefined

  at Runtime._createJestObjectFor (node_modules/jest-runner/node_modules/jest-runtime/build/index.js:734:35)
  at handle (node_modules/worker-farm/lib/child/index.js:44:8)
  at process.<anonymous> (node_modules/worker-farm/lib/child/index.js:51:3)
  at emitTwo (events.js:126:13)
  at process.emit (events.js:214:7)

I saw that someone had the same problem here (http://ift.tt/2D7psgj) but I'm not sure if it ever got resolved. I tried removing node_modules and reinstalling but that didn't fix it. Wondering if anyone else has had the same error before and how it got resolved?

Note: All of my client Jest tests pass correctly, but all of the server ones get this error.