private void verifyArcShown(String arcId, String sourceNodeId,
String targetNodeId) {
ArgumentCaptor<Arc> captor = ArgumentCaptor.forClass(Arc.class);
verify(graphDisplay, times(1)).addArc(captor.capture());
Arc result = captor.getValue();
assertEquals(arcId, result.getId());
assertEquals(sourceNodeId, result.getSourceNodeId());
assertEquals(targetNodeId, result.getTargetNodeId());
assertEquals(arcTypeId, result.getType());
}