TestScheduler expectObservable not respecting subscription marbles when using toEqual

[djonestru]

Describe the bug

When using expectObservable from the TestScheduler with subscription marbles:

const actual = createTestObservable();
const expected = createExpectedObservable();
expectObservable(actual,  '^---!').toEqual(expected);

When the ! marble is scheduled, only the expected observable will be unsubscribed and not the actual observable. This seems to be because the implementation shares the same subscription variable, so when expected is subscribed it overwrites the subscription from actual. Which means any custom teardown logic won't be run for actual.

Expected behavior

I'd expect the following asserts to be synonymous:

expectObservable(actual,  '^---!').toBe('1234');
expectObservable(actual,  '^---!').toEqual(cold('1234'));

Reproduction code

import { TestScheduler } from 'rxjs/testing';
import { isEqual } from 'lodash';
import { Observable } from 'rxjs';

describe('TestScheduler', () => {
  let testScheduler: TestScheduler;
  let disposed = false;

  beforeEach(() => {
    testScheduler = new TestScheduler(isEqual);
    disposed = false;
  });

  it('should unsubscribe toBe', () => {
    testScheduler.run(({ expectObservable }) => {
      expectObservable(
        new Observable((_) => () => (disposed = true)),
        '^!'
      ).toBe('');
    });
    expect(disposed).toBeTruthy();
  });

  // This fails.
  it('should unsubscribe toEqual', () => {
    testScheduler.run(({ cold, expectObservable }) => {
      expectObservable(
        new Observable((_) => () => (disposed = true)),
        '^!'
      ).toEqual(cold(''));
    });
    expect(disposed).toBeTruthy();
  });
});

Reproduction URL

https://stackblitz.com/edit/stackblitz-starters-bs79vc?file=TestScheduler.spec.ts

Version

8.0.0-alpha.12 and 7.8.1

Environment

No response

Additional context

No response