### Question:
FlowGraph { public Set<V> getVertices() { return Collections.unmodifiableSet(successors.keySet()); } FlowGraph(Map<V, Set<V>> edges, V entryPoint, V exitPoint); private  FlowGraph(FlowGraph<V> originalGraph); V getEntryPoint(); V getExitPoint(); Map<V, Set<V>> getSuccessors(); Map<V, Set<V>> getPredecessors(); Set<V> getVertices(); Set<V> getSuccessors(V vertex); Set<V> getPredecessors(V vertex); FlowGraph<V> getTransverseGraph(); Map<V, V> getImmediateDominators(); Map<V, Set<V>> getDominatorTree(); Map<V, Set<V>> getDominatorSets(); Map<V, Set<V>> getDominanceFrontiers(); Map<V, V> getImmediatePostDominators(); Map<V, Set<V>> getPostDominatorSets(); Map<V, Set<V>> getPostDominanceFrontiers(); Set<NaturalLoop<V>> getNaturalLoops(); boolean containsPath(V source, V target); @Override boolean equals(Object o); @Override int hashCode(); void write(Writer writer, String graphName, Comparator<V> vertexComparator,
                      Function<V, String> printer, int fontSize);  }### Answer:
@Test public void testGetVerticesEmptyGraph() { assertEquals(new HashSet<>(Arrays.asList(0, 1)), emptyGraph.getVertices()); }
@Test public void testGetVerticesLoopingGraph() { Set<Integer> expected = new HashSet<>(); for(int i = 0; i <= 11; i++) { expected.add(i); } assertEquals(expected, loopingGraph.getVertices()); }