mocha-vm

Run Mocha tests inside a vm2 sandbox environment and get the results as a JavaScript object.

This package makes it easy to use Mocha inside Node.js, allowing you to run untrusted Mocha code with Chai – securely!

Installation

IMPORTANT: Requires Node.js 6 or newer.

Using npm:

npm i mocha-vm

Using yarn:

yarn add mocha-vm

In Node.js:

const run = require('mocha-vm').run;
const toHTML = require('mocha-vm').toHTML;

// Or using ES6+ destructuring assignment syntax
const { run, toHTML } = require('mocha-vm');

Quick Example

const { run } = require('mocha-vm');

const code = `
describe('addOne', function () {
  it('should return 3 when the value is 2', function () {
    assert.equal(addOne(2), 3);
  });
  it('should return 0 when the value is -1', function () {
    assert.equal(addOne(-1), 0);
  });
  it('return a number', function () {
    assert.isNumber(addOne(-1));
  });
});

function addOne(x) {
  return x + 1;
};`;

run(code).then(obj => console.log(obj));

run(code[, options])

• code String | Array
• options String | Object
  • library String | Object (Default: 'chai')

The code argument can be a String (containing a code snippet or a file path) or an Array.

The options argument allows you to use Node.js's built-in 'assert' library, rather than 'chai' (the default). To do this, use:

run(code, { library: 'assert' });

Or simply:

run(code, 'assert');

toHTML(result)

• result Object

The toHTML function is a utility, allowing you to tranform the result of run into an HTML string, which can easily be displayed on the client-side.

run(code).then(result => {
    let html = toHTML(result);
    return html;
});

If using vanilla JavaScript, you can insert the HTML code like follows:

let node = document.createElement("section");
node.className = "mocha-result";
node.innerHTML = html;

document.querySelector("body").appendChild(node);

If using React, you can safely pass it into the dangerouslySetInnerHTML property:

<section className="mocha-result" dangerouslySetInnerHTML={{ __html: html }} />

Available Mocha and Chai Methods

By default, the code inside the string(s) can make use of:

• Chai's assert, expect and/or should libraries.
• Mocha's BDD methods, including describe, context, it, specify, before, after, beforeEach and afterEach.

To find out more about using these methods, visit the Mocha and Chai websites.

IMPORTANT: The methods and libraries above are imported in advance. Your code will not run if you try to re-import them.

Passing a File Path

To pass a file path, it's recommended to use Node.js's built-in 'path' module, as below:

const { run } = require('mocha-vm');
const { join } = require('path');

run(join(__dirname, 'tests.js')).then(obj => console.log(obj));

Passing an Array

You can pass an Array containing:

• only code snippets,
• only file paths,
• a mixture of the two.

For example:

const { run } = require('mocha-vm');
const { join } = require('path');

const test = `
describe('addOne', function () {
  it('should return 3 when the value is 2', function () {
    assert.equal(addOne(2), 3);
  });
});`;

const functionToTest = `
function addOne(x) {
  return x + 1;
};`;

run([test, functionToTest, join(__dirname, 'tests.js')]).then(obj =>
  console.log(obj)
);

Result

Aside from just running the tests, the run function returns a Promise containing the results of the tests. Using the tests from the Quick Example (above), we would get an object like this:

{
  "summary": {
    "passed": 3,
    "failed": 0,
    "tests": 3,
    "suites": 1,
    "depth": 0,
    "duration": "32ms"
  },
  "data": [
    {
      "depth": 0,
      "suite": "addOne",
      "tests": [
        {
          "description": "should return 3 when the value is 2",
          "passed": true
        },
        {
          "description": "should return 0 when the value is -1",
          "passed": true
        },
        { "description": "should return a number", "passed": true }
      ],
      "duration": "18ms"
    }
  ]
}

If we were to use the toHTML function and pass the object above as an argument, we would get the following HTML string:

<div class="mocha-item">
  <p class="mocha-suite">addOne</p>
  <p class="mocha-test passed">&nbsp;&nbsp;✓ should return 3 when the value is 2</p>
  <p class="mocha-test passed">&nbsp;&nbsp;✓ should return 0 when the value is -1</p>
  <p class="mocha-test passed">&nbsp;&nbsp;✓ should return a number</p>
</div>
<br>
<div class="mocha-summary">
  <p class="mocha-passing">3 passing <span class="mocha-duration">(32ms)</span></p>
  <p class="mocha-failing">0 failing</p>
</div>

Dependencies

This package depends on Mocha and Chai for testing, and vm2 for sandboxing.

Author

• Bret Cameron

License

This project is licensed under the MIT License.