Add component tests for ClassTree

[aadorian]

Description

Only three ontology components currently have tests (header, property-details, new-entity-dialog). ClassTree handles expand/collapse, selection, and sessionStorage persistence but is untested.

Difficulty

Easy–Medium

Skills

React Testing Library, Jest

Relevant files

• components/ontology/class-tree.tsx
• components/ontology/__tests__/class-tree.test.tsx (create)
• lib/ontology/sample-data.ts — sample ontology for mocks

Tasks

• Create components/ontology/__tests__/class-tree.test.tsx
• Test expand/collapse toggle on nodes with children
• Test "Expand all" and "Collapse all" toolbar buttons
• Test clicking a class row calls selectClass
• Mock useOntology with sample data

Acceptance Criteria

• All new tests pass with npm test
• No changes to production behavior required (tests only)
• Follow patterns in existing component tests

Getting started

1. Comment on this issue to get assigned
2. Fork the repo and create a branch: test/class-tree
3. Run npm ci && npm test before opening a PR