Issues #502 and #587- Add additional tests

[nikosbosse]

Description

This PR partly addresses #502.

As discussed in #502, this PR adds a few additional tests to score() in tests/testthat/test-score.R.
Addressing #502 raised two new issues (#800, #801). I suggest addressing #801 (done) and then adding more tests as suggested in #502.

This PR closes #587.
As discussed in #587, I went through all exported functions and added additional tests to make sure the output class is exactly what we expect it to be. In some places, I cleaned tests by

• moving headings around,
• removing duplicated tests
• adding small additional tests

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title as follows: issue-number: PR title
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• I have built the package locally and run rebuilt docs using roxygen2.
• My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[seabbs]

Nice looks good to me