Vitest for unit tests

[ngAlexander9]

Description

Implements infrastructure for writing unit tests for frontend. It's not fully covering all cases, but provides infrastructure and usage patterns for testing frontend business logic as well as UI components.

Motivation

Vitest seems to be a commonly used JS testing framework and goes well with our current usage of vite.

Unit test files are colocated with the component files they test. This seems to be a common organizational pattern, as it allows for shorter import statements, keeps tests and components close (and easier to navigate together), and promotes maintaining and adding to tests.

Screenshots

Pre-merge checklist

• Code works interactively
• Code follows the style guide
• Code contains descriptive docstrings
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions

[Copilot]

Pull request overview

Adds a Vitest + Testing Library setup to enable unit testing of the frontend (business-logic utilities and React components), with a shared render helper for React Query–dependent components.

Changes:

• Configure Vitest in vite.config.ts (jsdom, globals, setup file) and add test scripts/deps in package.json.
• Add shared test setup/utilities (src/test/setup.ts, src/test/render.tsx) and initial unit tests for utils/components.
• Update TypeScript/ESLint configuration to support test files and Vitest globals.

Reviewed changes

Copilot reviewed 9 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
vite.config.ts	Adds Vitest configuration (jsdom, setup file) and adjusts env logging during tests.
tsconfig.json	Updates compiler options/types to support Vitest globals and Node typings.
src/utils/tolerance.test.ts	Adds unit tests for tolerance helpers.
src/utils/csvParser.test.ts	Adds unit tests for CSV parsing/tag validation helpers.
src/test/setup.ts	Loads jest-dom matchers for tests.
src/test/render.tsx	Introduces renderWithProviders with a test QueryClient for React Query components.
src/components/TagGroupSelect.test.tsx	Adds component tests for TagGroupSelect behavior.
src/components/SearchBar.test.tsx	Adds component tests for SearchBar behavior (with icon mocks).
package.json	Adds Vitest + Testing Library deps and test scripts.
pnpm-lock.yaml	Locks new testing-related dependencies.
.gitignore	Adds a rule to ignore *.csv.
.eslintrc.cjs	Stops ignoring tests and adds overrides for Vitest globals in test files.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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