data-test attributes contain mixed-case values

Overview: data-test-... attributes must not contain mixed-case values in order to avoid console warnings.
Details: Mixed-case data-test-... attributes were added to some interactors in PR #154, but React assumes such attributes are react props and issues a console warning, e.g.

Warning: React does not recognize the `data-test-addressList-container` prop on a DOM element. If you intentionally want it to appear in the DOM as a custom attribute, spell it as lowercase `data-test-addresslist-container` instead. If you accidentally passed it from a parent component, remove it from the DOM element.