The following discussion from gitlab-org/gitlab-ui!691 should be addressed: - [ ] @adriel started a [discussion](https://gitlab.com/gitlab-org/gitlab-ui/merge_requests/691#note_203742338): (+4 comments) > The code looks great. My only comment would be whether we should add tests to make sure we are checking this default tooltip behavior. Snapshots won't test for this since it involves user interaction. When a users explicitly sets `tooltip: { trigger: 'axis' }` via the chart's `option` prop, the `defaultFormatTooltipText` won't work since in this case an array is passed to the function (instead of an object). Let's refactor `defaultFormatTooltipText` to account for both use cases.