「[Vue warn]: Unknown custom element: <nuxt-link> - did you register the component correctly? For recursive components, make sure to provide the "name" option.」が出たら「mount(Component, {stubs: ['nuxt-link']」などで対処。
「[Vue warn]: Unknown custom element: <nuxt-link> - did you register the component correctly? For recursive components, make sure to provide the "name" option.」「テストを書くと、aタグにレンダリングされないでnuxt-linkのままになってしまう」