WIP test for EmberJS accidentally creating cyclic structure in Array.prototype

test.js

import { NativeArray } from '../../lib/mixins/array';
import { AbstractTestCase, moduleFor } from 'internal-test-helpers';

class ArrayPrototypeExtensionSelfReferenceTests extends AbstractTestCase {
  '@test should not create non-Symbol, enumerable properties that refer to itself'() {
    // Don't want to pollute Array.prototype so we make our own to extend
    class ThrowAwayArray extends Array {}

    // Extend our throw-away prototype (like EXTEND_PROTOTYPES.Array would)
    NativeArray.apply(ThrowAwayArray.prototype);

    // Create an instance to test
    let obj = new ThrowAwayArray();

    // Home-made depth-first-search for cycle detection
    // Alternatively a module from npm (like 'is-circular' could be used instead)
    function isCyclic(node, path) {
      path = path || [];
      path.push(node);
      const root = path[0];

      for (let p in node) {
        const value = node[p];
        if (value === root) {
          return path.concat(p);
        }
        else if (typeof value === 'object') {
          try {
            const result = isCyclic(value, path);
            if (result) {
              return result;
            }
          } catch(e) {
            return true; 
          }
        }
      }
      return false;
    }
    // Make sure that no enumerable properties refer back to the object (creating a cyclic structure)
    const result = isCyclic(obj);
    this.assert.ok(
        result === false,
        `Detected a cyclic reference (${result}) on an enumerable part of the prototype.
        This is bad because it may break a lot of 3rd party code.
        For example, code that explores all properties,
        such as jQuery.extend and other "deep cloning" functions,
        will get stuck in an infinite loop.
        `.replace(/\s+/g, ' ')
    );
  }
}

moduleFor(`NativeArray: apply`, ArrayPrototypeExtensionSelfReferenceTests);