// Test successful heartbeat
        assertTrue(mockService.processHeartbeat(regId, 1));
        assertTrue(mockService.processHeartbeat(regId, 2));

        // Test heartbeat for non-existent registration
        assertFalse(mockService.processHeartbeat("non-existent", 1));

        // Clean up
        mockService.unregisterWitness(regId);
    }

    @Test