Migrate from jest to vitest

[katrynmc]

Migrate spectral to vitest and update fast-check (property based testing library) to latest.

This leaves jest-mock in place since we expose a util that uses it as a part of our public API.

I've adopted the vitest connector for fast-check which appears to be the preferred way to use the library. That necessitates a larger refactor of our usage but ultimately seems to land in a better spot.

Main:

This Branch:

[Copilot]

Pull request overview

This pull request migrates the Spectral testing framework from Jest to Vitest and updates fast-check to version 4.x with the Vitest connector integration. The migration maintains backward compatibility by keeping jest-mock as a dependency since it's part of the public API.

Changes:

• Replaced Jest with Vitest as the test runner
• Updated fast-check from 2.16.0 to 4.5.3 and adopted the @fast-check/vitest connector
• Refactored property-based tests to use it.prop syntax
• Updated test assertions for better type safety (toStrictEqual → toBe where appropriate)
• Removed TypeScript workaround that was needed for Jest

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Removed Jest dependencies, added Vitest and related packages
packages/spectral/vitest.config.ts	New Vitest configuration file
packages/spectral/tsconfig.test.json	Removed jest types, kept node types
packages/spectral/package.json	Updated test scripts and dev dependencies
packages/spectral/jest.config.js	Removed obsolete Jest configuration
packages/spectral/src/util.test.ts	Migrated to Vitest with it.prop pattern
packages/spectral/src/conditionalLogic/index.test.ts	Migrated to Vitest syntax
packages/spectral/src/serverTypes/*.test.ts	Updated mock usage (jest.fn → vi.fn)
packages/spectral/src/serverTypes/context.ts	Removed TypeScript error suppression workaround

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[misteroneill]

LGTM

[misteroneill]

nitpick: Definitely not a blocker. In a ternary with complex expressions, I like to use parentheses to ensure clarity:

const usage = showDetail ? memoryUsageInMB() : (memoryUsage.rss() / MEMORY_USAGE_CONVERSION);

Otherwise, even if we know how the interpreter will interpret it, a human reading it could interpret it as equivalent to:

const usage = (showDetail ? memoryUsageInMB() : memoryUsage.rss()) / MEMORY_USAGE_CONVERSION;

[katrynmc]

This is actually something I have no control over :D prettier (or biome in our case) takes this away