istanbul-lib-coverage 3.2.2: createCoverageMap, createFileCoverage, createCoverageSummary

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: verify pkg:npm/istanbul-lib-coverage@3.2.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/istanbul-lib-coverage@3.2.2
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:8b001030319e3ca89de1e47237bff48e36e39b0a0559516cce9102d13992130b","constraints":{"executionContext":"node"},"contract":["createCoverageMap creates an empty coverage map or initializes from raw coverage data","addFileCoverage registers FileCoverage instances and tracks mapped files","CoverageMap.filter modifies coverage map in-place retaining files matching filter predicate","createFileCoverage calculates line coverage, uncovered lines, and branch coverage metrics","FileCoverage.merge merges statement, function, and branch hits from another coverage record","FileCoverage.resetHits resets all execution hit counts to zero","createCoverageSummary calculates line, statement, function, and branch percentages","CoverageSummary.merge aggregates metrics across summaries and updates totals and percentages","CoverageMap.merge combines coverage data across multiple coverage maps"],"goal":"verify pkg:npm/istanbul-lib-coverage@3.2.2","kind":"HOW","packages":["pkg:npm/istanbul-lib-coverage@3.2.2"],"schemaVersion":1,"symbols":["createCoverageMap","createFileCoverage","createCoverageSummary"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/istanbul-lib-coverage@3.2.2"],"schemaVersion":1,"subject":"pkg:npm/istanbul-lib-coverage@3.2.2","symbols":["createCoverageMap","createFileCoverage","createCoverageSummary"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-istanbul-lib-coverage",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-istanbul-lib-coverage",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "istanbul-lib-coverage": "3.2.2"
      }
    },
    "node_modules/istanbul-lib-coverage": {
      "version": "3.2.2",
      "resolved": "https://registry.npmjs.org/istanbul-lib-coverage/-/istanbul-lib-coverage-3.2.2.tgz",
      "integrity": "sha512-O8dpsF+r0WV/8MNRKfnmrtCWhuKjxrq2w+jpzBL5UZKTi2LeVWnWOmWRxFlesJONmc+wLAGvKQZEOanko0LFTg==",
      "license": "BSD-3-Clause",
      "engines": {
        "node": ">=8"
      }
    }
  }
}

{
  "name": "sample-istanbul-lib-coverage",
  "version": "1.0.0",
  "private": true,
  "description": "verify pkg:npm/istanbul-lib-coverage@3.2.2",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "istanbul-lib-coverage": "3.2.2"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/istanbul-lib-coverage@3.2.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/istanbul-lib-coverage@3.2.2"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

'use strict';

const istanbulCoverage = require('istanbul-lib-coverage');
const { createCoverageMap, createFileCoverage, createCoverageSummary, classes } = istanbulCoverage;

/**
 * Creates an empty or pre-populated coverage map.
 * @param {Object} [data]
 * @returns {istanbulCoverage.CoverageMap}
 */
function createMap(data) {
  return createCoverageMap(data);
}

/**
 * Creates a file coverage object.
 * @param {string|Object} pathOrObj
 * @returns {istanbulCoverage.FileCoverage}
 */
function createFile(pathOrObj) {
  return createFileCoverage(pathOrObj);
}

/**
 * Creates an empty or pre-populated coverage summary.
 * @param {Object} [data]
 * @returns {istanbulCoverage.CoverageSummary}
 */
function createSummary(data) {
  return createCoverageSummary(data);
}

/**
 * Merges multiple coverage maps into a single new coverage map.
 * @param {istanbulCoverage.CoverageMap[]} maps
 * @returns {istanbulCoverage.CoverageMap}
 */
function mergeMaps(maps) {
  const merged = createCoverageMap({});
  for (const m of maps) {
    merged.merge(m);
  }
  return merged;
}

/**
 * Adds file coverage with hit counts to a coverage map.
 * @param {istanbulCoverage.CoverageMap} map
 * @param {string} filePath
 * @param {Object} statementMap
 * @param {Object} statementHits
 * @param {Object} [fnMap]
 * @param {Object} [fnHits]
 * @param {Object} [branchMap]
 * @param {Object} [branchHits]
 * @returns {istanbulCoverage.FileCoverage}
 */
function addFileRecord(map, filePath, statementMap, statementHits, fnMap = {}, fnHits = {}, branchMap = {}, branchHits = {}) {
  const fc = createFileCoverage({
    path: filePath,
    statementMap,
    fnMap,
    branchMap,
    s: statementHits,
    f: fnHits,
    b: branchHits
  });
  map.addFileCoverage(fc);
  return fc;
}

/**
 * Calculates aggregated summary for the entire coverage map.
 * @param {istanbulCoverage.CoverageMap} map
 * @returns {Object}
 */
function getSummaryMetrics(map) {
  const summary = map.getCoverageSummary();
  return {
    lines: summary.lines,
    statements: summary.statements,
    functions: summary.functions,
    branches: summary.branches,
    isEmpty: summary.isEmpty()
  };
}

module.exports = {
  createCoverageMap,
  createFileCoverage,
  createCoverageSummary,
  classes,
  createMap,
  createFile,
  createSummary,
  mergeMaps,
  addFileRecord,
  getSummaryMetrics
};

'use strict';

const assert = require('node:assert');
const istanbulCoverage = require('istanbul-lib-coverage');
const {
  createCoverageMap,
  createFileCoverage,
  createCoverageSummary,
  classes,
  createMap,
  createFile,
  createSummary,
  mergeMaps,
  addFileRecord,
  getSummaryMetrics
} = require('../src/index.js');

function testCreateCoverageMap() {
  // Empty coverage map
  const map = createCoverageMap();
  assert.strictEqual(Array.isArray(map.files()), true);
  assert.strictEqual(map.files().length, 0);

  // Add file coverage
  const fc1 = createFileCoverage({
    path: 'lib/module-a.js',
    statementMap: {
      '0': { start: { line: 1, column: 0 }, end: { line: 1, column: 20 } },
      '1': { start: { line: 2, column: 0 }, end: { line: 2, column: 20 } }
    },
    fnMap: {
      '0': { name: 'greet', decl: { start: { line: 1, column: 0 }, end: { line: 1, column: 20 } }, loc: { start: { line: 1, column: 0 }, end: { line: 1, column: 20 } }, line: 1 }
    },
    branchMap: {},
    s: { '0': 1, '1': 0 },
    f: { '0': 1 },
    b: {}
  });

  map.addFileCoverage(fc1);
  assert.deepStrictEqual(map.files(), ['lib/module-a.js']);

  const retrieved = map.fileCoverageFor('lib/module-a.js');
  assert.ok(retrieved instanceof classes.FileCoverage);
  assert.strictEqual(retrieved.path, 'lib/module-a.js');

  // Serialization to JSON
  const json = map.toJSON();
  assert.ok(json['lib/module-a.js']);

  // Filter map mutates in place
  map.filter((filePath) => filePath.endsWith('module-a.js'));
  assert.deepStrictEqual(map.files(), ['lib/module-a.js']);

  map.filter((filePath) => filePath.endsWith('nonexistent.js'));
  assert.strictEqual(map.files().length, 0);
}

function testFileCoverageCalculations() {
  const fc = createFileCoverage({
    path: 'lib/calc.js',
    statementMap: {
      '0': { start: { line: 1, column: 0 }, end: { line: 1, column: 15 } },
      '1': { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
      '2': { start: { line: 3, column: 0 }, end: { line: 3, column: 15 } }
    },
    fnMap: {
      '0': { name: 'add', decl: { start: { line: 1, column: 0 }, end: { line: 1, column: 15 } }, loc: { start: { line: 1, column: 0 }, end: { line: 1, column: 15 } }, line: 1 }
    },
    branchMap: {
      '0': {
        loc: { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
        type: 'if',
        locations: [
          { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
          { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } }
        ],
        line: 2
      }
    },
    s: { '0': 2, '1': 1, '2': 0 },
    f: { '0': 2 },
    b: { '0': [1, 0] }
  });

  const lineCov = fc.getLineCoverage();
  assert.strictEqual(lineCov['1'], 2);
  assert.strictEqual(lineCov['2'], 1);
  assert.strictEqual(lineCov['3'], 0);

  const uncovered = fc.getUncoveredLines();
  assert.deepStrictEqual(uncovered, ['3']);

  const branchCov = fc.getBranchCoverageByLine();
  assert.deepStrictEqual(branchCov['2'], { covered: 1, total: 2, coverage: 50 });

  const summary = fc.toSummary();
  assert.strictEqual(summary.lines.total, 3);
  assert.strictEqual(summary.lines.covered, 2);
  assert.strictEqual(summary.statements.total, 3);
  assert.strictEqual(summary.statements.covered, 2);
  assert.strictEqual(summary.functions.total, 1);
  assert.strictEqual(summary.functions.covered, 1);
  assert.strictEqual(summary.branches.total, 2);
  assert.strictEqual(summary.branches.covered, 1);

  // Merge another run into fc
  const fc2 = createFileCoverage({
    path: 'lib/calc.js',
    statementMap: {
      '0': { start: { line: 1, column: 0 }, end: { line: 1, column: 15 } },
      '1': { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
      '2': { start: { line: 3, column: 0 }, end: { line: 3, column: 15 } }
    },
    fnMap: {},
    branchMap: {
      '0': {
        loc: { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
        type: 'if',
        locations: [
          { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } },
          { start: { line: 2, column: 0 }, end: { line: 2, column: 15 } }
        ],
        line: 2
      }
    },
    s: { '0': 0, '1': 0, '2': 3 },
    f: {},
    b: { '0': [0, 1] }
  });

  fc.merge(fc2);
  const mergedSummary = fc.toSummary();
  assert.strictEqual(mergedSummary.lines.covered, 3);
  assert.strictEqual(mergedSummary.statements.covered, 3);
  assert.strictEqual(mergedSummary.branches.covered, 2);

  // Reset hits
  fc.resetHits();
  const resetSummary = fc.toSummary();
  assert.strictEqual(resetSummary.lines.covered, 0);
  assert.strictEqual(resetSummary.statements.covered, 0);
  assert.strictEqual(resetSummary.functions.covered, 0);
}

function testCoverageSummaryAndMerging() {
  const summary1 = createCoverageSummary({
    lines: { total: 10, covered: 8, skipped: 0, pct: 80 },
    statements: { total: 10, covered: 8, skipped: 0, pct: 80 },
    functions: { total: 4, covered: 3, skipped: 0, pct: 75 },
    branches: { total: 6, covered: 3, skipped: 0, pct: 50 }
  });
  assert.strictEqual(summary1.isEmpty(), false);

  const summary2 = createCoverageSummary({
    lines: { total: 10, covered: 10, skipped: 0, pct: 100 },
    statements: { total: 10, covered: 10, skipped: 0, pct: 100 },
    functions: { total: 2, covered: 2, skipped: 0, pct: 100 },
    branches: { total: 4, covered: 4, skipped: 0, pct: 100 }
  });

  summary1.merge(summary2);
  assert.strictEqual(summary1.lines.total, 20);
  assert.strictEqual(summary1.lines.covered, 18);
  assert.strictEqual(summary1.statements.total, 20);
  assert.strictEqual(summary1.statements.covered, 18);
  assert.strictEqual(summary1.functions.total, 6);
  assert.strictEqual(summary1.functions.covered, 5);
  assert.strictEqual(summary1.branches.total, 10);
  assert.strictEqual(summary1.branches.covered, 7);
  assert.strictEqual(summary1.lines.pct, 90);
}

function testCoverageMapMerging() {
  const map1 = createCoverageMap();
  addFileRecord(
    map1,
    'src/feature1.js',
    { '0': { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } } },
    { '0': 1 },
    { '0': { name: 'f1', decl: { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } }, loc: { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } }, line: 1 } },
    { '0': 1 }
  );

  const map2 = createCoverageMap();
  addFileRecord(
    map2,
    'src/feature2.js',
    { '0': { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } } },
    { '0': 0 },
    { '0': { name: 'f2', decl: { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } }, loc: { start: { line: 1, column: 0 }, end: { line: 1, column: 10 } }, line: 1 } },
    { '0': 0 }
  );

  const mergedMap = mergeMaps([map1, map2]);
  assert.deepStrictEqual(mergedMap.files().sort(), ['src/feature1.js', 'src/feature2.js']);

  const metrics = getSummaryMetrics(mergedMap);
  assert.strictEqual(metrics.lines.total, 2);
  assert.strictEqual(metrics.lines.covered, 1);
  assert.strictEqual(metrics.lines.pct, 50);
  assert.strictEqual(metrics.statements.total, 2);
  assert.strictEqual(metrics.statements.covered, 1);
  assert.strictEqual(metrics.functions.total, 2);
  assert.strictEqual(metrics.functions.covered, 1);
  assert.strictEqual(metrics.isEmpty, false);
}

function run() {
  testCreateCoverageMap();
  testFileCoverageCalculations();
  testCoverageSummaryAndMerging();
  testCoverageMapMerging();
  console.log('Contract tests passed successfully.');
  process.exit(0);
}

run();