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Ejemplo

istanbul-lib-instrument 5.2.1: instrument JavaScript code using createInstrumenter and extract file coverage

Muestra verificada para npm istanbul-lib-instrument 5.2.1: instrument JavaScript code using createInstrumenter and extract file coverage. El contrato se…

sha256:bfa376c68822a758666e350b24a139ef117d54fc5964eed4400f7a406a2b1aca

Esta red ofrece una sola cosa: una muestra que compila. La ejecutó en un sandbox y guardó el recibo firmado. No califica ni garantiza nada: si el mismo código compila donde estás no es algo que haya medido. Cuántas claves de firma distintas presentaron un recibo de contrato aprobado. Una es solo el autor; más de una significa que alguien más también lo compiló. Una clave se genera sola y no tiene identidad registrada detrás, así que cuenta claves, no personas. MIT-0

Evidencia de ejecución

El entorno declarado y las ejecuciones firmadas se muestran por separado, para que veas exactamente qué ejecutó esta muestra y dónde.

Base de evidencia
Contrato firmado aprobado
Recibos de verificación
1
Claves de firma que lo compilaron
1
Entorno declarado linux 24 · ubuntu · glibc 2.39 x64 npm

Entornos de las ejecuciones de verificación

Entorno Contrato Etapas Ejecución
node 22 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22-alpine@sha256:c610fcdfb1d5…		 2026-08-26

Caso

HOW
Objetivo
instrument JavaScript code using createInstrumenter and extract file coverage
Paquetes
Símbolos
  • createInstrumenter
  • instrumentSync
  • lastFileCoverage
Creado
2026-08-26T14:13:56Z

Contrato

  1. assert createInstrumenter creates an instrumenter with instrumentSync, lastFileCoverage, and lastSourceMap methods
  2. assert instrumentSync transforms JavaScript source code to include coverage counters and initial metadata referencing coverageVariable
  3. assert lastFileCoverage returns FileCoverageData structure with statementMap, fnMap, branchMap, and initial zero counts
  4. assert lastSourceMap returns generated source map when produceSourceMap is enabled
  5. assert readInitialCoverage extracts initial file coverage metadata from instrumented code
  6. assert instrumentSync throws an error on invalid JavaScript syntax
  7. assert executing instrumented code in a JavaScript runtime VM records statement hit counts

Archivos

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.mjs
  • test/contract.mjs

Descargar el artefacto de código fuente (tar.gz)

Código fuente

PROMPT.md
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: instrument JavaScript code using createInstrumenter and extract file coverage
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/istanbul-lib-instrument@5.2.1
Demonstrate these symbols/APIs:
  - createInstrumenter
  - instrumentSync
  - lastFileCoverage

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.
csx.json
{"case":{"caseId":"case:sha256:23180788d269e07e48dc453ddb1448b241312df94a3c25de39af9affc4e4a257","contract":["assert createInstrumenter creates an instrumenter with instrumentSync, lastFileCoverage, and lastSourceMap methods","assert instrumentSync transforms JavaScript source code to include coverage counters and initial metadata referencing coverageVariable","assert lastFileCoverage returns FileCoverageData structure with statementMap, fnMap, branchMap, and initial zero counts","assert lastSourceMap returns generated source map when produceSourceMap is enabled","assert readInitialCoverage extracts initial file coverage metadata from instrumented code","assert instrumentSync throws an error on invalid JavaScript syntax","assert executing instrumented code in a JavaScript runtime VM records statement hit counts"],"goal":"instrument JavaScript code using createInstrumenter and extract file coverage","kind":"HOW","packages":["pkg:npm/istanbul-lib-instrument@5.2.1"],"schemaVersion":1,"symbols":["createInstrumenter","instrumentSync","lastFileCoverage"]},"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/istanbul-lib-instrument@5.2.1"],"schemaVersion":1,"subject":"pkg:npm/istanbul-lib-instrument@5.2.1","symbols":["createInstrumenter","instrumentSync","lastFileCoverage"],"verifierAdapter":"node-typescript@1"}
package-lock.json
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package.json
{
  "name": "csx-sample-istanbul-lib-instrument",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "istanbul-lib-instrument": "5.2.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "instrument JavaScript code using createInstrumenter and extract file coverage",
  "kind": "HOW",
  "packages": [
    "pkg:npm/istanbul-lib-instrument@5.2.1"
  ],
  "symbols": [
    "createInstrumenter",
    "instrumentSync",
    "lastFileCoverage"
  ]
}
src/index.mjs
import { createInstrumenter, programVisitor, readInitialCoverage } from 'istanbul-lib-instrument';

export { createInstrumenter, programVisitor, readInitialCoverage };

/**
 * Instruments JavaScript source code and extracts file coverage metadata.
 *
 * @param {string} code - The JavaScript source code to instrument.
 * @param {string} filename - The file path / identifier associated with the code.
 * @param {object} [options={}] - Options passed to createInstrumenter.
 * @returns {{ code: string, fileCoverage: object, sourceMap: object|null }}
 */
export function instrumentCode(code, filename, options = {}) {
  const instrumenter = createInstrumenter({
    coverageVariable: '__coverage__',
    preserveComments: true,
    compact: false,
    esModules: true,
    produceSourceMap: true,
    ...options,
  });

  const instrumentedCode = instrumenter.instrumentSync(code, filename);
  const fileCoverage = instrumenter.lastFileCoverage();
  const sourceMap = instrumenter.lastSourceMap();

  return {
    code: instrumentedCode,
    fileCoverage,
    sourceMap,
  };
}

/**
 * Creates an instrumenter instance with customized coverage variable and settings.
 *
 * @param {object} [options={}] - Instrumenter options.
 * @returns {object} - Istanbul instrumenter instance.
 */
export function createCustomInstrumenter(options = {}) {
  return createInstrumenter({
    coverageVariable: '__coverage__',
    preserveComments: true,
    ...options,
  });
}
test/contract.mjs
import { strict as assert } from 'node:assert';
import vm from 'node:vm';
import {
  createInstrumenter,
  programVisitor,
  readInitialCoverage,
  instrumentCode,
  createCustomInstrumenter,
} from '../src/index.mjs';

// 1. Verify module exports and types
assert.equal(typeof createInstrumenter, 'function', 'createInstrumenter must be a function');
assert.equal(typeof programVisitor, 'function', 'programVisitor must be a function');
assert.equal(typeof readInitialCoverage, 'function', 'readInitialCoverage must be a function');

// 2. Verify instrumenter instance creation and method availability
const instrumenter = createInstrumenter({
  coverageVariable: '__coverage__',
  preserveComments: true,
  produceSourceMap: true,
});
assert.equal(typeof instrumenter.instrumentSync, 'function', 'instrumenter must have instrumentSync method');
assert.equal(typeof instrumenter.lastFileCoverage, 'function', 'instrumenter must have lastFileCoverage method');
assert.equal(typeof instrumenter.lastSourceMap, 'function', 'instrumenter must have lastSourceMap method');

// 3. Instrument a sample JavaScript code snippet containing functions and branches
const filename = 'math.js';
const sampleCode = `
function add(a, b) {
  if (a > 0) {
    return a + b;
  }
  return b;
}
add(2, 3);
`;

const instrumented = instrumenter.instrumentSync(sampleCode, filename);
assert.equal(typeof instrumented, 'string', 'instrumentSync must return instrumented code string');
assert(instrumented.includes('__coverage__'), 'Instrumented code must reference coverage variable');
assert(instrumented.includes('path'), 'Instrumented code must contain coverage initialization');

// 4. Verify lastFileCoverage structure and metadata
const coverage = instrumenter.lastFileCoverage();
assert.ok(coverage, 'lastFileCoverage must return coverage data');
assert.equal(coverage.path, filename, 'Coverage path must match instrumented filename');
assert.ok(typeof coverage.statementMap === 'object', 'Coverage must have statementMap');
assert.ok(typeof coverage.fnMap === 'object', 'Coverage must have fnMap');
assert.ok(typeof coverage.branchMap === 'object', 'Coverage must have branchMap');
assert.ok(typeof coverage.s === 'object', 'Coverage must have statement hit counts');
assert.ok(typeof coverage.f === 'object', 'Coverage must have function hit counts');
assert.ok(typeof coverage.b === 'object', 'Coverage must have branch hit counts');

// Initial hit counters must be 0
for (const key of Object.keys(coverage.s)) {
  assert.equal(coverage.s[key], 0, `Statement counter ${key} must initially be 0`);
}
for (const key of Object.keys(coverage.f)) {
  assert.equal(coverage.f[key], 0, `Function counter ${key} must initially be 0`);
}
for (const key of Object.keys(coverage.b)) {
  for (const branchCount of coverage.b[key]) {
    assert.equal(branchCount, 0, `Branch counter ${key} must initially be 0`);
  }
}

// 5. Verify lastSourceMap generation
const sourceMap = instrumenter.lastSourceMap();
assert.ok(sourceMap, 'lastSourceMap must return a valid source map when produceSourceMap is true');
assert.equal(typeof sourceMap.version, 'number', 'Source map must have a version number');

// 6. Verify readInitialCoverage extracts initial coverage metadata
const initialCoverage = readInitialCoverage(instrumented);
assert.ok(initialCoverage, 'readInitialCoverage must extract coverage object from instrumented code');
assert.equal(initialCoverage.path, filename, 'Extracted initial coverage path must match');

// 7. Verify instrumentCode helper with ES modules and options
const esmSnippet = `
export function multiply(x, y) {
  return x * y;
}
`;
const result = instrumentCode(esmSnippet, 'calc.js', { esModules: true, produceSourceMap: true });
assert.ok(result.code.includes('multiply'), 'Instrumented ESM code must contain function name');
assert.equal(result.fileCoverage.path, 'calc.js', 'File coverage path must match calc.js');
assert.ok(result.sourceMap, 'Source map must be generated');

// 8. Verify instrumentSync throws error on syntax error
const invalidCode = `function invalid( { return ;`;
assert.throws(
  () => {
    instrumenter.instrumentSync(invalidCode, 'invalid.js');
  },
  (err) => {
    return err instanceof Error;
  },
  'instrumentSync must throw an error when given syntactically invalid code'
);

// 9. Verify instrumented code execution in VM records coverage hits
const execSnippet = `
function compute(n) {
  if (n > 5) {
    return n * 2;
  }
  return n;
}
compute(10);
`;
const inst2 = createInstrumenter({ coverageVariable: '__custom_cov__' });
const instCode2 = inst2.instrumentSync(execSnippet, 'compute.js');
const sandbox = { __custom_cov__: {} };
vm.createContext(sandbox);
vm.runInContext(instCode2, sandbox);

const recordedCoverage = sandbox.__custom_cov__['compute.js'];
assert.ok(recordedCoverage, 'Sandbox coverage variable must record coverage for compute.js');
assert.ok(recordedCoverage.s['0'] >= 1 || recordedCoverage.s['1'] >= 1, 'Statement hit counters must be incremented upon execution');

console.log('CONTRACT PASS: istanbul-lib-instrument createInstrumenter, instrumentSync, and lastFileCoverage verified');

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