Minimal test coverage

Since there have been several new modules added both through our own API extensions and ported from the official OpenDSS, we need to add a lot more tests to achieve some minimum coverage of the new features.

Start by reviewing the new modules added through the API extensions and ports from official OpenDSS, then compare them with the repository's existing test coverage. Add tests for the new features and verify that the project reaches an agreed minimum coverage level; the issue does not name specific files, tests, or a threshold.

Written by the indexing model from the issue text.