Most probably when updating package dependency, "babel-core"
dependency may have been updated to 6.xx.x
, it should be "7.0.0-bridge.0"
for jest to work.
Reference:
https://github.com/vuejs/vue-cli/issues/1879#issuecomment-412300256
https://github.com/vuejs/vue-cli/issues/1879#issuecomment-435194932