Behavior change in speech-rule-engine 3.2?

I'm using the speech-rule-engine to generate English text from MathML. When trying to upgrade from v3.1.1 to v3.2.0 I'm seeing tests fail for reasons I don't understand.

I created a simple two file project that illustrates the issue:

package.json

{
  "name": "failure-example",
  "license": "UNLICENSED",
  "private": true,
  "engines": {
    "node": "14.15.5",
    "npm": "6.14.11"
  },
  "scripts": {
    "test": "jest"
  },
  "dependencies": {
    "speech-rule-engine": "3.2.0"
  },
  "devDependencies": {
    "jest": "^26.6.3"
  },
  "jest": {
    "notify": false,
    "silent": true,
    "verbose": true
  }
}

example.test.js

const sre = require('speech-rule-engine');

beforeAll(() => {
    sre.setupEngine({
        domain: 'mathspeak'
    });
});

test('simple single math', () => {
    expect(JSON.parse(JSON.stringify(sre.engineSetup(), ['domain', 'locale', 'speech', 'style'])))
        .toEqual({
            locale: 'en',
            speech: 'none',
            style: 'default',
            domain: 'mathspeak',
        });
    expect(sre.engineReady())
        .toBeTruthy();
    expect(sre.toSpeech('<math><mrow><msup><mn>3</mn><mn>7</mn></msup></mrow></math>'))
        .toBe('3 Superscript 7');
});

Running npm install and npm run test results in a failure because SRE is returning 37 instead of 3 Superscript 7. Editing package.json to use v3.1.1 of the engine and rerunning results in a passing test.

Obviously something has changed, but I'm totally missing what I need to do to adapt. Has anyone else encountered this, or see what I clearly do not?

Solution

Problem solved, with the help of the maintainer of SRE. The problem is not in 3.2.0, but that jest does not wait for sre to be ready. The test was only correct by a fluke in 3.1.1 as the rules were compiled into the core. The following test fails with the above setup in 3.1.1 as well as the locale is not loaded:

expect(sre.toSpeech('<math><mo>=</mo></math>'))
        .toBe('equals');

    Expected: "equals"
    Received: "="

The main reason is that jest fails to load the locale file. Setting "silent": false will show the error:

 Unable to load file: /tmp/tests/node_modules/speech-rule-engine/lib/mathmaps/en.js
      TypeError: Cannot read property 'readFileSync' of null

The reason for this error is that jest does not know that it runs in node. Adding:

    "testEnvironment": "node",

to the jest configuration in package.json causes the expected behavior.