### Question:
MapUTGraph implements UTGraph<L, T>, HasPersistentNodes, HasPersistentLinks { @Override public long numLinks() { return numLinks; } MapUTGraph(); static MapUTGraph<L, T> copy(UTGraph<L, T> graph); static MapUTGraph<L,T> copy(UGraph<L> graph); @Override UTNode<L, T> node(L label); int size(); @Override Set<? extends UTNode<L, T>> nodes(L label); @Override UTNode<L, T> add(L label); boolean uniqueLabels(); String toString(); @Override boolean connected(L first, L second); @Override Set<L> labels(); @Override long numLinks(); @Override long state(); @Override List<? extends UTNode<L, T>> nodes(); @Override Iterable<MapUTLink> links(); @Override Set<T> tags(); @Override int hashCode(); @Override boolean equals(Object other); @Override UTNode<L, T> get(int i); @Override Class<? extends UTGraph<L, T>> level();  }### Answer:
@Test public void testNumLinks() { UGraph<String> graph = Examples.yeast(); int numLinks = 0; for(Link<String> link : graph.links()) numLinks++; assertEquals(2277, graph.numLinks()); assertEquals(graph.numLinks(), numLinks); }