Flaky `Cannot assign to read only property 'owner' of object '#<Context>'`

[rreckonerr]

Cannot assign to read only property 'owner' of object '#<Context>'

I'm upgrading test suit from ember-cli-mocha to ember-mocha 0.15.1 and get randomly failing tests all over again and those tests look fine when I'm running them separately. Is there a way to find out what's causing this error?

[rreckonerr]

Mentioned error appears because of some tests being started before the previous one is finished, which results in tests getting wrong originalContext and not being able to clean it up properly. Is my assumption correct? Any ideas how can I debug this further?

  beforeEach(function () {
    originalContext = _assign({}, this);
    console.group(
      `${originalContext.test.parent.title} => ${originalContext.currentTest.title}`
    );
    return setupContext(this, options)
      .then(() => setupPauseTest(this))
      .then(() => chainHooks(beforeEachHooks, this));
  });

  afterEach(function () {
    return chainHooks(afterEachHooks, this)
      .then(() => teardownContext(this))
      .then(() => {
        // delete any extraneous properties
        for (let key in this) {
          if (!(key in originalContext)) {
            console.log("key to delete :>> ", key);
            delete this[key];
          }
        }

        // copy over the original values
        _assign(this, originalContext);
      })
      .catch((error) => {
        console.log("this :>> ", this);
        console.log("originalContext :>> ", originalContext);
        console.error(error);
      })
      .finally(() => {
        console.groupEnd();
      });
  });

Example in the screenshot is failing randomly.

[notchris]

Can confirm this issue occurs