test: Do testing with jest instead of mocha for paginator

[danieljbruce]

Description

Migrates the @google-cloud/paginator package test suite and configuration from Mocha, Sinon, and c8 to Jest and ts-jest.

Key changes include:

• Dependency & Infrastructure Updates:
  • Removed legacy test dependencies (mocha, @types/mocha, sinon, @types/sinon, c8, proxyquire, @types/proxyquire).
  • Added jest, ts-jest, and @types/jest.
  • Added jest.config.js configured with ts-jest.
  • Removed .nycrc and updated .gitignore for coverage/.
  • Updated package.json test script to use jest --coverage.
• Test Suite Migration:
  • Migrated test/index.ts and test/resource-stream.ts to native Jest assertions (expect(...).toBe(), expect(...).toEqual(), etc.).
  • Replaced proxyquire and Sinon sandboxes/stubs/spies/timers with jest.mock(), jest.spyOn(), jest.fn(), and jest.useFakeTimers().
  • Modernized asynchronous test cases to use async/await and wrapped callback-based done() handlers in try/catch blocks to prevent hanging on test failures.

commits were migrated from #9218 to pass the cla check.

Impact

• Maintainability & Consistency: Aligns @google-cloud/paginator with repository-wide efforts to standardize test infrastructure on Jest.
• Developer Experience: Faster test execution, native TypeScript handling via ts-jest, and integrated code coverage reporting.
• No Runtime Impact: Purely internal test and development dependency changes; no public APIs or runtime behaviors were modified.

[gemini-code-assist]

Code Review

This pull request migrates the testing framework for the core/paginator package from Mocha, Sinon, and Proxyquire to Jest and ts-jest. This involves updating configuration files, replacing test scripts, and rewriting test assertions and mocks to use Jest's native capabilities. Feedback on these changes highlights a major version mismatch in package.json between jest (v30) and ts-jest (v29), suggesting a downgrade to version 29 for compatibility. Additionally, the newly introduced uuid and @types/uuid dependencies are unused and should be removed to prevent unnecessary bloat.

[gemini-code-assist]

This PR introduces a couple of issues in devDependencies:

1. Jest Version Mismatch: There is a major version mismatch between jest (^30.4.2) / @types/jest (^30.0.0) and ts-jest (^29.4.10). ts-jest major versions must align with the jest major version to prevent compatibility issues and runtime errors. Since Jest 30 is not yet stable, it is highly recommended to downgrade jest and @types/jest to version 29.
2. Unused Dependencies: Both uuid and @types/uuid have been added to devDependencies, but they are not imported or used anywhere in the codebase (the tests use the built-in crypto.randomUUID()). They should be removed to avoid unnecessary bloat.

    "@types/jest": "^29.5.12",
    "@types/node": "^22.13.8",
    "gts": "^6.0.2",
    "jest": "^29.7.0",
    "jsdoc": "^4.0.4",
    "jsdoc-fresh": "^6.0.0",
    "jsdoc-region-tag": "^5.0.0",
    "linkinator": "^6.1.2",
    "path-to-regexp": "^8.2.0",
    "ts-jest": "^29.4.10",
    "typescript": "^5.8.2"

References

1. When managing dependencies in package.json, ensure that @types packages are kept in sync with the major version of their corresponding main packages.

[danieljbruce]

Made these dependency modifications

[danieljbruce]

This is the only thing I'm a bit skeptical about because I've seen cases where a very particular subset of methods need to be faked, but its probably fine.

[feywind]

I hit a few of those. The specific issue was that sinon started hooking stuff like nextTick(), so it was breaking tests that literally just wanted to finish on the next tick. If jest didn't make that change, it should be completely fine. If it did, we might still have to look at those.