Looking through the stack trace I see this.$q is undefined when the LoadingBar plugin tries to install:
I’d imagine this is because the tests are using createLocalVue and therefore Quasar ($q) has been installed on the localVue but not on the instance created below:
One way around this (that’s worked for me) would therefore be to Vue.use(Quasar) to install Quasar globally before using createLocalVue.
However given that the installed Quasar $q is available in LoadingBar.install, I wonder whether it can be in some way used in the new Vue constructor; or indeed whether the localVue could be used in place of the Vue (although I don’t see a readily available reference to the localVue within that scope), thereby avoiding polluting the global Vue.