Add graph tests, bring coverage to 100%

[fstoerkle]

Description of new feature, or changes

Increase test coverage for graph.js

Checklist

• [x] Your branch is up-to-date with the base branch
• [x] You've included at least one test if this is a new feature
• [x] All tests are passing

Related Issues and Discussions

Made progress on #30

People to notify

@manrajgrover

[fstoerkle]

🎉