Methods on ES6 class instances don't get mocked

[AsaAyers]

ES6 class methods are not enumerable, so they aren't being mocked by Jest.

I'm using Babel to do the transforms.

// es6_class.js
class Foo {
    foo() { return 'foo'; }
    bar() { return 'bar'; }
}
module.exports = new Foo();
// I can assign a prop to make it interable, then it gets mocked
module.exports.bar = module.exports.bar;

// __tests__/es6_class.js
describe('es6 class instance', function() {
    let instance;
    beforeEach(function() {
        instance = require('../es6_class.js');
    });
    it('has foo', function() {
        expect(instance.foo).toBeTruthy();
    });
    it('has bar', function() {
        // This one works only because I reassigned it.
        expect(instance.bar).toBeTruthy();
    });
});

I also tried exporting the class and that fails even more spectacularly. I can't even create an instance of that mock.

[AsaAyers]

I thought maybe I could use Object.getOwnPropertyNames and Object.getOwnPropertyDescriptor to scan for the missing methods, but I couldn't get it to distinguish between foo above and built in methods.

For testing, if instead of checking the descriptor I just check that the prop === 'foo' then it fixes the code above. So I think if the filtering can be fixed it looks like a reasonable strategy.

var scan = function(obj) {
    var fakeObj = {};
    var prop;
    for (prop in obj) {
        fakeObj[prop] = true;
    }
    if (obj) {
        var props = [];
        var tmp = obj;
        var descriptor;
        do {
            props = Object.getOwnPropertyNames(tmp);

            for (var i = 0; i < props.length; i++) {
                prop = props[i];
                descriptor = Object.getOwnPropertyDescriptor(tmp, prop);
                // Try to find ES6 methods
                if (descriptor && !descriptor.enumerable && typeof descriptor.value === 'function') {
                    fakeObj[prop] = true;
                    // console.log(prop)
                    // This picks up many methods that can't be included:
                    // constructor
                    // toString
                    // toLocaleString
                    // valueOf
                    // hasOwnProperty
                    // isPrototypeOf
                    // propertyIsEnumerable
                    // __defineGetter__
                    // __lookupGetter__
                    // __defineSetter__
                    // __lookupSetter__
                    // Symbol(tie)_r.fdrvaoikracbx1or
                }
            }
        } while (tmp = Object.getPrototypeOf(tmp));
    }
    return fakeObj;
};

// from my local lib/moduleMocker.js
          for (var slot in scan(prototype)) { // line 109
    for (var slot in scan(metadata.members)) { // line 233
      for (var slot in scan(component)) { // line 295
      for (var slot in scan(metadata.members)) { // line 331

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