https://github.com/cssinjs/jss-snapshot-serializer

index.js

const MARKER = '__jss-snapshot-serializer-marker__';

const jssClassNameRegexp = /(^(?:[^-]+)-\w+)(?:(?:-\d+){1,2})/i;

const collectElements = (element, elements = []) => {
  if (typeof element !== 'object') {
    return elements;
  }

  elements.push(element);

  if (element.children) {
    element.children.forEach(child => collectElements(child, elements));
  }

  return elements;
};

const markElements = nodes => nodes.forEach((element) => {
  element[MARKER] = true;
});

const replaceJssClassNames = (elements) => {
  elements.forEach((element) => {
    if (!element.props || !element.props.class) return;

    const classNameProp = element.props.class;

    const deterministicClassNames = classNameProp
      .trim()
      .split(/\s+/)
      .map((className) => {
        console.log('className', className, jssClassNameRegexp.test(className))
        console.log('jssClassNameRegexp.exec(className)', jssClassNameRegexp.exec(className))
        // do not modify the className if it is not generated by JSS
        if (!jssClassNameRegexp.test(className)) return className;

        return jssClassNameRegexp.exec(className)[1]
      });

    element.props.class = deterministicClassNames.join(' ');
  });
};


module.exports = {
  test(value) {
    // apply the serializer only to react elements that we haven't marked(processed) before
    return value && !value[MARKER] && value.$$typeof === Symbol.for('react.test.json');
  },

  print(value, serialize) {
    // collect all react element nodes in the tree of the value
    const elements = collectElements(value);

    // mark the collected element nodes to avoid processing them several times
    markElements(elements);

    // remove the non-deterministic part from the JSS class names
    // to keep the snapshots repeatable
    replaceJssClassNames(elements);

    return serialize(value);
  },
};