test: migrate from AVA to Vitest and remove test macros (#221)

Replace AVA test framework with Vitest and eliminate all test macros
by expanding them into explicit, self-documenting test cases. This
migration improves developer experience with watch mode, built-in
coverage reporting, and makes each test independently readable.

Key changes:

Dependencies and Configuration:
- Replace AVA with Vitest for test execution
- Remove NYC in favor of Vitest's built-in coverage (@vitest/coverage-v8)
- Remove eslint-plugin-ava and add eslint-plugin-vitest
- Create vitest.config.js with ES Modules support, parallel execution,
  and coverage configuration matching previous NYC settings
- Configure coverage to generate html, lcov, and text reports in a
  single test run

Test Migration (153 test files transformed):
- Convert all test files from AVA syntax to Vitest syntax
- Replace AVA's `t.deepEqual()` with `expect().toEqual()`
- Replace AVA's `t.truthy()` with `expect().toBeTruthy()`
- Replace AVA's `t.throws()` with `expect().toThrow()`
- Use explicit imports: `import { test, expect, describe } from 'vitest'`

Test Macro Elimination:
- Remove test/_macros.js entirely (contained 6 test macro patterns)
- Expand `setsAggType` macro into explicit aggregation type tests
- Expand `validatedCorrectly` macro into table-driven validation tests
- Expand `makeSetsOptionMacro` generated tests into explicit option tests
- Expand `illegalCall` macro into explicit error tests with toThrow()
- Expand `illegalParamType` macro into explicit TypeError tests
- All expanded tests follow table-driven patterns for maintainability

Test Utilities:
- Create test/testutil/ package for shared test helper functions
- Add type checking utilities for parameter validation
- Export all utilities from test/testutil/index.js
- Reuse existing recursiveToJSON from src/core/util.js

Package Scripts:
- Update test:src: `vitest run --coverage` (single-step execution)
- Remove report script (now redundant with Vitest)
- Remove coverage script (now redundant with Vitest)
- Add test:watch: `vitest` for local development with watch mode
- Keep test:typedef unchanged for TypeScript type checking

ESLint Configuration:
- Remove plugin:ava/recommended from test/.eslintrc.yml
- Add plugin:vitest/recommended to test/.eslintrc.yml
- Update plugins array to use vitest instead of ava

CI/CD:
- Update .github/workflows/build.yml to use `npm test` instead of
  separate `npm run coverage` (coverage now generated during test run)
- Maintain testing on Node.js 20.x, 22.x, 24.x
- Preserve Coveralls integration with lcov format

Bug Fixes:
- Remove src/suggesters/phase-suggester.js (incorrectly named file,
  should be phrase-suggester.js which already exists)

Documentation:
- Update README.md with new test commands using Vitest
- Update CONTRIBUTING.md with Vitest test instructions
- Add test/testing-guidelines.mdc for test writing guidelines

This migration maintains test coverage while improving code clarity
and developer experience. All 153 test files now use explicit,
self-documenting test cases instead of opaque macro invocations.

Author: sudo-suhas

.github/workflows/build.yml

@@ -31,9 +31,7 @@ jobs:
       - name: Install dependencies
         run: npm ci
       - name: Check
-        run: |
-          npm run check
-          npm run coverage
+        run: npm run check
       - name: Coveralls
         uses: coverallsapp/[email protected]
         with:

CONTRIBUTING.md

@@ -35,13 +35,25 @@ elastic-builder is published to npm.
 
 ### Run tests
 
-This project uses eslint for javascript linting and ava for testing. Run
-linting using `npm run lint` and run tests using `npm run test`. Or run both using:
+This project uses eslint for javascript linting and vitest for testing. Run
+linting using `npm run lint` and run tests using `npm test`. Or run both using:
 ```
 npm run check
 ```
 This should take care of formatting as well thanks to [eslint-plugin-prettier][3].
 
+You can also run tests in watch mode during development:
+```
+npm run test:watch
+```
+
+To generate coverage reports:
+```
+npm run test:src
+```
+
+Coverage reports are generated in the `coverage/` directory.
+
 ### (Optional) Add yourself as a contributor
 
 Thanks for contributing! Go ahead and add yourself to the list of contributors

README.md

@@ -367,6 +367,20 @@ Run unit tests:
 npm test
 ```
 
+Run tests in watch mode:
+
+```
+npm run test:watch
+```
+
+Run tests with coverage:
+
+```
+npm run test:src
+```
+
+Coverage reports are generated in the `coverage/` directory.
+
 ## Credits
 
 `elastic-builder` is heavily inspired by [`elastic.js`][elastic-js] and the