jest-util 30.4.1: isPromise

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 jest-util.isPromise in pkg:npm/jest-util@30.4.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/jest-util@30.4.1
Demonstrate these symbols/APIs:
  - jest-util.isPromise

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:sha256:4cbb39f7c34b7842a34081720820199794bbf2bc304626f0b109aa1aead137d2","contract":["isPromise returns true for native Promise instances","isPromise returns true for async function return values","isPromise returns true for custom thenable objects with a then method","isPromise returns true for functions that implement a then method","isPromise returns false for null and undefined","isPromise returns false for primitive values","isPromise returns false for plain objects and arrays without a then method","isPromise returns false for objects where then property is not a function","isPromise returns false for standard functions without a then method","jest-util exports isPromise in both CommonJS and ECMAScript module formats"],"goal":"verify jest-util.isPromise in pkg:npm/jest-util@30.4.1","kind":"HOW","packages":["pkg:npm/jest-util@30.4.1"],"schemaVersion":1,"symbols":["jest-util.isPromise"]},"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/jest-util@30.4.1"],"schemaVersion":1,"subject":"pkg:npm/jest-util@30.4.1","symbols":["jest-util.isPromise"],"verifierAdapter":"node-typescript@1"}

import { isPromise } from 'jest-util';

export { isPromise };

{
  "name": "sample-jest-util-ispromise",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-jest-util-ispromise",
      "version": "1.0.0",
      "dependencies": {
        "jest-util": "30.4.1"
      }
    },
    "node_modules/@jest/pattern": {
      "version": "30.4.0",
      "resolved": "https://registry.npmjs.org/@jest/pattern/-/pattern-30.4.0.tgz",
      "integrity": "sha512-RAWn3+f9u8BsHijKJ71uHcFp6vmyEt6VvoWXkl6hKF3qVIuWNmudVjg12DlBPGup/frIl5UcUlH5HfEuvHpEXg==",
      "license": "MIT",
      "dependencies": {
        "@types/node": "*",
        "jest-regex-util": "30.4.0"
      },
      "engines": {
        "node": "^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0"
      }
    },
    "node_modules/@jest/schemas": {
      "version": "30.4.1",
      "resolved": "https://registry.npmjs.org/@jest/schemas/-/schemas-30.4.1.tgz",
      "integrity": "sha512-i6b4qw5qnP8c5FEeBJg/uZQ4ddrkN6Ca8qISJh0pr7a5hfn3h3v5x60BEbOC7OYAGZNMs1LfFLwnW2CuK8F57Q==",
      "license": "MIT",
      "dependencies": {
        "@sinclair/typebox": "^0.34.0"
      },
      "engines": {
        "node": "^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0"
      }
    },
    "node_modules/@jest/types": {
      "version": "30.4.1",
      "resolved": "https://registry.npmjs.org/@jest/types/-/types-30.4.1.tgz",
      "integrity": "sha512-f1x/vJXIfjOlEmejYpbkbgw1gOqpPECwMvMEtBqe47j7H2Hg8h8w3o3ikhSXq3MI15kg+oQ0exWO0uCtTNJLoQ==",
      "license": "MIT",
      "dependencies": {
        "@jest/pattern": "30.4.0",
        "@jest/schemas": "30.4.1",
        "@types/istanbul-lib-coverage": "^2.0.6",
        "@types/istanbul-reports": "^3.0.4",
        "@types/node": "*",
        "@types/yargs": "^17.0.33",
        "chalk": "^4.1.2"
      },
      "engines": {
        "node": "^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0"
      }
    },
    "node_modules/@sinclair/typebox": {
      "version": "0.34.52",
      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.34.52.tgz",
      "integrity": "sha512-XiMQh7qqVlxZzcVD+kkGMNGMzcTrDMLWI7S4x7z1MkCkbDPrekpZXEUK0eZqZFMuHQg2a2DZOcDIh9o5v3Gonw==",
      "license": "MIT"
    },
    "node_modules/@types/istanbul-lib-coverage": {
      "version": "2.0.6",
      "resolved": "https://registry.npmjs.org/@types/istanbul-lib-coverage/-/istanbul-lib-coverage-2.0.6.tgz",
      "integrity": "sha512-2QF/t/auWm0lsy8XtKVPG19v3sSOQlJe/YHZgfjb/KBBHOGSV+J2q/S671rcq9uTBrLAXmZpqJiaQbMT+zNU1w==",
      "license": "MIT"
    },
    "node_modules/@types/istanbul-lib-report": {
      "version": "3.0.3",
      "resolved": "https://registry.npmjs.org/@types/istanbul-lib-report/-/istanbul-lib-report-3.0.3.tgz",
      "integrity": "sha512-NQn7AHQnk/RSLOxrBbGyJM/aVQ+pjj5HCgasFxc0K/KhoATfQ/47AyUl15I2yBUpihjmas+a+VJBOqecrFH+uA==",
      "license": "MIT",
      "dependencies": {
        "@types/istanbul-lib-coverage": "*"
      }
    },
    "node_modules/@types/istanbul-reports": {
      "version": "3.0.4",
      "resolved": "https://registry.npmjs.org/@types/istanbul-reports/-/istanbul-reports-3.0.4.tgz",
      "integrity": "sha512-pk2B1NWalF9toCRu6gjBzR69syFjP4Od8WRAX+0mmf9lAjCRicLOWc+ZrxZHx/0XRjotgkF9t6iaMJ+aXcOdZQ==",
      "license": "MIT",
      "dependencies": {
        "@types/istanbul-lib-report": "*"
      }
    },
    "node_modules/@types/node": {
      "version": "26.4.1",
      "resolved": "https://registry.npmjs.org/@types/node/-/node-26.4.1.tgz",
      "integrity": "sha512-k97ENvZWtvA6yqz5/FS6a7duDgOPEeOQOc2iKS/nY6mX6qJUKtLnWzQS+Xj6tXweyj6ZcTAK2Qecetnvi9nCLA==",
      "license": "MIT",
      "dependencies": {
        "undici-types": "~8.3.0"
      }
    },
    "node_modules/@types/yargs": {
      "version": "17.0.35",
      "resolved": "https://registry.npmjs.org/@types/yargs/-/yargs-17.0.35.tgz",
      "integrity": "sha512-qUHkeCyQFxMXg79wQfTtfndEC+N9ZZg76HJftDJp+qH2tV7Gj4OJi7l+PiWwJ+pWtW8GwSmqsDj/oymhrTWXjg==",
      "license": "MIT",
      "dependencies": {
        "@types/yargs-parser": "*"
      }
    },
    "node_modules/@types/yargs-parser": {
      "version": "21.0.3",
      "resolved": "https://registry.npmjs.org/@types/yargs-parser/-/yargs-parser-21.0.3.tgz",
      "integrity": "sha512-I4q9QU9MQv4oEOz4tAHJtNz1cwuLxn2F3xcc2iV5WdqLPpUnj30aUuxt1mAxYTG+oe8CZMV/+6rU4S4gRDzqtQ==",
      "license": "MIT"
    },
    "node_modules/ansi-styles": {
      "version": "4.3.0",
      "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-4.3.0.tgz",
      "integrity": "sha512-zbB9rCJAT1rbjiVDb2hqKFHNYLxgtk8NURxZ3IZwD3F6NtxbXZQCnnSi1Lkx+IDohdPlFp222wVALIheZJQSEg==",
      "license": "MIT",
      "dependencies": {
        "color-convert": "^2.0.1"
      },
      "engines": {
        "node": ">=8"
      },
      "funding": {
        "url": "https://github.com/chalk/ansi-styles?sponsor=1"
      }
    },
    "node_modules/chalk": {
      "version": "4.1.2",
      "resolved": "https://registry.npmjs.org/chalk/-/chalk-4.1.2.tgz",
      "integrity": "sha512-oKnbhFyRIXpUuez8iBMmyEa4nbj4IOQyuhc/wy9kY7/WVPcwIO9VA668Pu8RkO7+0G76SLROeyw9CpQ061i4mA==",
      "license": "MIT",
      "dependencies": {
        "ansi-styles": "^4.1.0",
        "supports-color": "^7.1.0"
      },
      "engines": {
        "node": ">=10"
      },
      "funding": {
        "url": "https://github.com/chalk/chalk?sponsor=1"
      }
    },
    "node_modules/ci-info": {
      "version": "4.4.0",
      "resolved": "https://registry.npmjs.org/ci-info/-/ci-info-4.4.0.tgz",
      "integrity": "sha512-77PSwercCZU2Fc4sX94eF8k8Pxte6JAwL4/ICZLFjJLqegs7kCuAsqqj/70NQF6TvDpgFjkubQB2FW2ZZddvQg==",
      "funding": [
        {
          "type": "github",
          "url": "https://github.com/sponsors/sibiraj-s"
        }
      ],
      "license": "MIT",
      "engines": {
        "node": ">=8"
      }
    },
    "node_modules/color-convert": {
      "version": "2.0.1",
      "resolved": "https://registry.npmjs.org/color-convert/-/color-convert-2.0.1.tgz",
      "integrity": "sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==",
      "license": "MIT",
      "dependencies": {
        "color-name": "~1.1.4"
      },
      "engines": {
        "node": ">=7.0.0"
      }
    },
    "node_modules/color-name": {
      "version": "1.1.4",
      "resolved": "https://registry.npmjs.org/color-name/-/color-name-1.1.4.tgz",
      "integrity": "sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==",
      "license": "MIT"
    },
    "node_modules/graceful-fs": {
      "version": "4.2.11",
      "resolved": "https://registry.npmjs.org/graceful-fs/-/graceful-fs-4.2.11.tgz",
      "integrity": "sha512-RbJ5/jmFcNNCcDV5o9eTnBLJ/HszWV0P73bc+Ff4nS/rJj+YaS6IGyiOL0VoBYX+l1Wrl3k63h/KrH+nhJ0XvQ==",
      "license": "ISC"
    },
    "node_modules/has-flag": {
      "version": "4.0.0",
      "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-4.0.0.tgz",
      "integrity": "sha512-EykJT/Q1KjTWctppgIAgfSO0tKVuZUjhgMr17kqTumMl6Afv3EISleU7qZUzoXDFTAHTDC4NOoG/ZxU3EvlMPQ==",
      "license": "MIT",
      "engines": {
        "node": ">=8"
      }
    },
    "node_modules/jest-regex-util": {
      "version": "30.4.0",
      "resolved": "https://registry.npmjs.org/jest-regex-util/-/jest-regex-util-30.4.0.tgz",
      "integrity": "sha512-mWlvLviKIgIQ8VCuM1xRdD0TWp3zlzionlmDBjuXVBs+VkmXq6FgW9T4Emr7oGz/Rk6feDCGyiugolcQEyp3mg==",
      "license": "MIT",
      "engines": {
        "node": "^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0"
      }
    },
    "node_modules/jest-util": {
      "version": "30.4.1",
      "resolved": "https://registry.npmjs.org/jest-util/-/jest-util-30.4.1.tgz",
      "integrity": "sha512-vjQb1sACEiv13DKJMDToJpzVW0joCsIQrmbg0fi7CyOOt+g9jTuQl2A216pWRBYhOVt53XbL/2LbMKg1BECWOw==",
      "license": "MIT",
      "dependencies": {
        "@jest/types": "30.4.1",
        "@types/node": "*",
        "chalk": "^4.1.2",
        "ci-info": "^4.2.0",
        "graceful-fs": "^4.2.11",
        "picomatch": "^4.0.3"
      },
      "engines": {
        "node": "^18.14.0 || ^20.0.0 || ^22.0.0 || >=24.0.0"
      }
    },
    "node_modules/picomatch": {
      "version": "4.0.7",
      "resolved": "https://registry.npmjs.org/picomatch/-/picomatch-4.0.7.tgz",
      "integrity": "sha512-qcJu88Q2IWqJsDD529JKMdwGm/dvInW4HvQnRwiH9JtihJvzGOscDtHE3x1pBKeUOTysQ8kVmLnJ2kJu7yhcGA==",
      "license": "MIT",
      "engines": {
        "node": ">=12"
      },
      "funding": {
        "url": "https://github.com/sponsors/jonschlinkert"
      }
    },
    "node_modules/supports-color": {
      "version": "7.2.0",
      "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-7.2.0.tgz",
      "integrity": "sha512-qpCAvRl9stuOHveKsn7HncJRvv501qIacKzQlO/+Lwxc9+0q2wLyv4Dfvt80/DPn2pqOBsJdDiogXGR9+OvwRw==",
      "license": "MIT",
      "dependencies": {
        "has-flag": "^4.0.0"
      },
      "engines": {
        "node": ">=8"
      }
    },
    "node_modules/undici-types": {
      "version": "8.3.0",
      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-8.3.0.tgz",
      "integrity": "sha512-j375ScV60dom+YkPFIfTLcOiPxkN/buHz5GobjLhixFuANaNs3C9l4GmrWqejgXWJ7BbJcFYpTEUkS1Ge8bpZQ==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-jest-util-ispromise",
  "version": "1.0.0",
  "description": "Clean-room verification sample for jest-util isPromise",
  "type": "module",
  "private": true,
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "jest-util": "30.4.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify jest-util.isPromise in pkg:npm/jest-util@30.4.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/jest-util@30.4.1"
  ],
  "symbols": [
    "jest-util.isPromise"
  ]
}

import assert from 'node:assert/strict';
import { createRequire } from 'node:module';
import { isPromise } from 'jest-util';
import { isPromise as isPromiseFromLocal } from '../index.mjs';

const require = createRequire(import.meta.url);

// 1. isPromise returns true for native Promise instances
{
  assert.equal(isPromise(Promise.resolve('resolved')), true);
  assert.equal(isPromise(new Promise(() => {})), true);
  assert.equal(isPromise(Promise.reject('rejected').catch(() => {})), true);
}

// 2. isPromise returns true for async function return values
{
  async function sampleAsyncFunction() {
    return 'value';
  }
  const promiseInstance = sampleAsyncFunction();
  assert.equal(isPromise(promiseInstance), true);
  promiseInstance.catch(() => {});
}

// 3. isPromise returns true for custom thenable objects with a then method
{
  const thenableObject = {
    then(onFulfilled) {
      if (typeof onFulfilled === 'function') {
        onFulfilled('done');
      }
    },
  };
  assert.equal(isPromise(thenableObject), true);
}

// 4. isPromise returns true for functions that implement a then method
{
  function callableWithThen() {}
  callableWithThen.then = function (onFulfilled) {
    if (typeof onFulfilled === 'function') {
      onFulfilled();
    }
  };
  assert.equal(isPromise(callableWithThen), true);
}

// 5. isPromise returns false for null and undefined
{
  assert.equal(isPromise(null), false);
  assert.equal(isPromise(undefined), false);
}

// 6. isPromise returns false for primitive values
{
  const primitives = [
    0,
    1,
    -1,
    0n,
    42n,
    '',
    'then',
    'promise',
    true,
    false,
    Symbol('promise'),
    Symbol.for('then'),
  ];
  for (const val of primitives) {
    assert.equal(isPromise(val), false);
  }
}

// 7. isPromise returns false for plain objects and arrays without a then method
{
  assert.equal(isPromise({}), false);
  assert.equal(isPromise({ foo: 'bar' }), false);
  assert.equal(isPromise([]), false);
  assert.equal(isPromise([1, 2, 3]), false);
  assert.equal(isPromise(new Date()), false);
  assert.equal(isPromise(new Map()), false);
  assert.equal(isPromise(new Set()), false);
}

// 8. isPromise returns false for objects where then property is not a function
{
  assert.equal(isPromise({ then: null }), false);
  assert.equal(isPromise({ then: undefined }), false);
  assert.equal(isPromise({ then: 'string' }), false);
  assert.equal(isPromise({ then: 123 }), false);
  assert.equal(isPromise({ then: true }), false);
  assert.equal(isPromise({ then: {} }), false);
}

// 9. isPromise returns false for standard functions without a then method
{
  function regularFunction() {}
  assert.equal(isPromise(regularFunction), false);
  assert.equal(isPromise(() => {}), false);
  assert.equal(isPromise(async () => {}), false);
}

// 10. jest-util exports isPromise in both CommonJS and ECMAScript module formats
{
  assert.equal(typeof isPromise, 'function');
  assert.equal(isPromise, isPromiseFromLocal);

  const cjs = require('jest-util');
  assert.equal(typeof cjs.isPromise, 'function');
  assert.equal(cjs.isPromise, isPromise);
}

console.log('All jest-util.isPromise contract assertions passed successfully.');