// Verify callback was used correctly
        assertEquals(2, callback.getDocumentSize());
        assertTrue(callback.isCommitted());
    }

    @Test
    public void test_multiple_datastore_instances() {
        // Test multiple DataStore instances working independently
        final AtomicInteger store1CallCount = new AtomicInteger(0);
        final AtomicInteger store2CallCount = new AtomicInteger(0);