@bcoe/v8-coverage 0.2.3: merge multiple V8 process coverage reports with mergeProcessCovs

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: merge multiple V8 process coverage reports with mergeProcessCovs
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40bcoe/v8-coverage@0.2.3
Demonstrate these symbols/APIs:
  - mergeProcessCovs

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:48f7b7e6c6976410c5973fd8c2d959d22d18bfe34fb298cb006fa724728481a6","contract":["import mergeProcessCovs and cloneProcessCov from @bcoe/v8-coverage","merge multiple V8 ProcessCov reports containing multiple scripts and functions","assert script URLs are matched and scriptId values are normalized sequentially","assert execution counts for corresponding function root and branch ranges are summed across runs","assert scripts unique to a single run are preserved in the merged ProcessCov output"],"goal":"merge multiple V8 process coverage reports with mergeProcessCovs","kind":"HOW","packages":["pkg:npm/%40bcoe/v8-coverage@0.2.3"],"schemaVersion":1,"symbols":["mergeProcessCovs"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40bcoe/v8-coverage@0.2.3"],"schemaVersion":1,"subject":"pkg:npm/%40bcoe/v8-coverage@0.2.3","symbols":["mergeProcessCovs"],"verifierAdapter":"node-typescript@1"}

{
  "name": "csx-sample-v8-coverage-merge-process-covs",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "csx-sample-v8-coverage-merge-process-covs",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "@bcoe/v8-coverage": "0.2.3"
      }
    },
    "node_modules/@bcoe/v8-coverage": {
      "version": "0.2.3",
      "resolved": "https://registry.npmjs.org/@bcoe/v8-coverage/-/v8-coverage-0.2.3.tgz",
      "integrity": "sha512-0hYQ8SB4Db5zvZB4axdMHGwEaQjkZzFjQiN9LVYvIFB2nSUHW9tYpxWriPrWDASIxiaXax83REcLxuSdnGPZtw==",
      "license": "MIT"
    }
  }
}

{
  "name": "csx-sample-v8-coverage-merge-process-covs",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "@bcoe/v8-coverage": "0.2.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "merge multiple V8 process coverage reports with mergeProcessCovs",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40bcoe/v8-coverage@0.2.3"
  ],
  "symbols": [
    "mergeProcessCovs"
  ]
}

import { mergeProcessCovs, cloneProcessCov } from '@bcoe/v8-coverage';

/**
 * Merges multiple V8 process coverage objects into a single normalized report.
 *
 * @param {Array<import('@bcoe/v8-coverage').ProcessCov>} processReports
 * @returns {import('@bcoe/v8-coverage').ProcessCov}
 */
export function mergeCoverageReports(processReports) {
  // mergeProcessCovs mutates input objects; clone them to prevent unintended side effects
  const cloned = processReports.map(report => cloneProcessCov(report));
  return mergeProcessCovs(cloned);
}

import { strict as assert } from 'node:assert';
import { mergeCoverageReports } from '../src/index.mjs';

// Define coverage data from two separate test runs covering multiple scripts and functions
const run1 = {
  result: [
    {
      scriptId: '10',
      url: 'file:///workspace/math.js',
      functions: [
        {
          functionName: 'add',
          isBlockCoverage: true,
          ranges: [{ startOffset: 0, endOffset: 50, count: 2 }]
        },
        {
          functionName: 'divide',
          isBlockCoverage: true,
          ranges: [
            { startOffset: 60, endOffset: 150, count: 1 },
            { startOffset: 90, endOffset: 130, count: 0 }
          ]
        }
      ]
    },
    {
      scriptId: '11',
      url: 'file:///workspace/util.js',
      functions: [
        {
          functionName: 'identity',
          isBlockCoverage: true,
          ranges: [{ startOffset: 0, endOffset: 40, count: 5 }]
        }
      ]
    }
  ]
};

const run2 = {
  result: [
    {
      scriptId: '20',
      url: 'file:///workspace/math.js',
      functions: [
        {
          functionName: 'add',
          isBlockCoverage: true,
          ranges: [{ startOffset: 0, endOffset: 50, count: 3 }]
        },
        {
          functionName: 'divide',
          isBlockCoverage: true,
          ranges: [
            { startOffset: 60, endOffset: 150, count: 2 },
            { startOffset: 90, endOffset: 130, count: 2 }
          ]
        }
      ]
    }
  ]
};

const merged = mergeCoverageReports([run1, run2]);

// 1. Verify script normalization and merging across scripts
assert.equal(merged.result.length, 2);

const mathScript = merged.result.find(s => s.url === 'file:///workspace/math.js');
assert.ok(mathScript, 'math.js script report must exist');
assert.equal(mathScript.scriptId, '0');

const utilScript = merged.result.find(s => s.url === 'file:///workspace/util.js');
assert.ok(utilScript, 'util.js script report must exist');
assert.equal(utilScript.scriptId, '1');

// 2. Verify function 'add' counts were summed (2 + 3 = 5)
const addFn = mathScript.functions.find(f => f.functionName === 'add');
assert.ok(addFn, 'add function must exist');
assert.equal(addFn.ranges[0].count, 5);

// 3. Verify function 'divide' root range (1 + 2 = 3) and branch range (0 + 2 = 2)
const divideFn = mathScript.functions.find(f => f.functionName === 'divide');
assert.ok(divideFn, 'divide function must exist');
const rootDivide = divideFn.ranges.find(r => r.startOffset === 60 && r.endOffset === 150);
assert.ok(rootDivide, 'divide root range must exist');
assert.equal(rootDivide.count, 3);

const branchDivide = divideFn.ranges.find(r => r.startOffset === 90 && r.endOffset === 130);
assert.ok(branchDivide, 'divide branch range must exist');
assert.equal(branchDivide.count, 2);

// 4. Verify script present only in run1 is preserved unchanged
const idFn = utilScript.functions.find(f => f.functionName === 'identity');
assert.ok(idFn, 'identity function must exist');
assert.equal(idFn.ranges[0].count, 5);

console.log('CONTRACT PASS: mergeProcessCovs merged process coverage reports successfully');