 = collection.getSnapshotAt(scopedId, 15);
    assert.strictEqual(s2.args.foo, 1);
    assert.strictEqual(s1, s2);

    const s3 = collection.getSnapshotAt(scopedId, 20);
    assert.strictEqual(s3.args.foo, 2);
    assert.strictEqual(s1.object, s3.object);

    const s4 = collection.getSnapshotAt(scopedId, 25);
    assert.strictEqual(s4, s3);
  });

  test('twoObjectsSharingOneID', function() {
    const collection = new tr.model.ObjectCollection({});
    const scopedId = new tr.model.ScopedId('ptr', '0x100