@Test
    public void testGetConnectionsToPriorMassesOnConnectedMasses() {
        graph.addMasses(mass1, mass2);
        graph.addSpring(mass2, mass1);

        assertEquals("", GraphConverter.getConnectionsToPriorMasses(mass1, graph));
        assertEquals(",0", GraphConverter.getConnectionsToPriorMasses(mass2, graph));
    }