@Test
 public void addGraph_incompatibleSelfLoopConfig() {
   try {
     UndirectedGraph graph = Graphs.createUndirected(Graphs.config().noSelfLoops());
     ImmutableUndirectedGraph.Builder immutableGraphBuilder = ImmutableUndirectedGraph.builder();
     immutableGraphBuilder.addGraph(graph);
     fail("Should have rejected a graph with an incompatible self-loop configuration");
   } catch (IllegalArgumentException expected) {
   }
 }
 @Test
 public void addGraph_incompatibleMultigraphConfig() {
   try {
     UndirectedGraph multigraph = Graphs.createUndirected(Graphs.MULTIGRAPH);
     ImmutableUndirectedGraph.Builder immutableGraphBuilder = ImmutableUndirectedGraph.builder();
     immutableGraphBuilder.addGraph(multigraph);
     fail("Should have rejected a graph with an incompatible multigraph configuration");
   } catch (IllegalArgumentException expected) {
   }
 }
 @Override
 public ImmutableUndirectedGraph<Integer, String> createGraph() {
   builder = ImmutableUndirectedGraph.builder(Graphs.config().noSelfLoops());
   return builder.build();
 }