feat: Set up frontend unit testing framework and write component tests

[aGallea]

Problem

The frontend has no unit test framework configured. Only Playwright E2E tests exist (e2e/search.spec.ts). Issue #12 (Cluster Drill-Down and Annotation) specified frontend component tests as a requirement, but the infrastructure to run them does not exist.

Proposed Solution

1. Set up Vitest + React Testing Library + jsdom

Install and configure:

• vitest as the test runner
• @testing-library/react + @testing-library/jest-dom for component testing
• jsdom as the test environment
• @testing-library/user-event for user interaction simulation

Add vitest.config.ts and a test:unit script to package.json.

2. Write component tests for issue #12 features

ClusterDetailDrawer.test.tsx

• Renders drawer with cluster items (metadata, thumbnails)
• Pagination controls work correctly
• Inline cluster name editing
• Notes textarea updates
• Tags input
• Calls correct API functions on interaction

SubClusterView.test.tsx

• Renders mini scatter plot with sub-cluster data
• Sub-cluster count selector triggers re-computation
• Handles loading and error states

ClusterLegend.test.tsx

• Click on cluster name opens detail drawer (not just toggle visibility)
• Visibility toggle checkbox still works independently
• Shows annotation indicator when cluster has notes

plotStore.test.ts

• openClusterDetail() action fetches and stores cluster items
• subCluster() action triggers sub-cluster computation
• updateAnnotation() action persists annotation changes
• selectedCluster and clusterItems derived state

3. Add to CI

Add a test:unit job to .github/workflows/ci.yml that runs npm run test:unit in the frontend directory.

Acceptance Criteria

• Vitest + React Testing Library configured and working
• npm run test:unit script added to package.json
• Component tests for ClusterDetailDrawer, SubClusterView, ClusterLegend
• Store tests for plotStore drill-down and annotation actions
• CI job runs frontend unit tests
• All tests pass

Related

• Spawned from feat: Cluster Drill-Down and Annotation #12 (Cluster Drill-Down and Annotation) — frontend test requirement