Improve pinned items components' specs

The following discussion from !113292 (merged) should be addressed:

• @ohoral started a discussion:

  It is not advised to test the vm properties. It is better to test what was rendered

  expect(wrapper.findComponent(PinnedSections).exists()).toBe(true);

  And it looks like the tests for other components are missing.

  Given that it will be a lot of change do you think we should create a follow-up, e.g. "Improve pinned items components' specs" that you or other engineer could pick up?