### Question:
GraphRelation extends AbstractBaseGraphObject implements IMutableGraphRelation { @Nonnull @ReturnsMutableCopy public ICommonsOrderedSet <IMutableGraphNode> getAllConnectedNodes () { return new CommonsLinkedHashSet <> (m_aNode1, m_aNode2); } GraphRelation(@Nonnull final IMutableGraphNode aNode1, @Nonnull final IMutableGraphNode aNode2);  GraphRelation(@Nullable final String sID, @Nonnull final IMutableGraphNode aNode1, @Nonnull final IMutableGraphNode aNode2); final boolean isDirected(); boolean isRelatedTo(@Nullable final IMutableGraphNode aNode); @Nonnull @ReturnsMutableCopy ICommonsOrderedSet <IMutableGraphNode> getAllConnectedNodes(); @Nonnull @ReturnsMutableCopy ICommonsOrderedSet <String> getAllConnectedNodeIDs(); @Nonnull IMutableGraphNode getNode1(); @Nonnull IMutableGraphNode getNode2(); @Override boolean equals(final Object o); @Override int hashCode(); @Override String toString();  }### Answer:
@Test public void testGet () { final GraphNode nf = new GraphNode (); final GraphNode nt = new GraphNode (); final GraphRelation gr = new GraphRelation (nf, nt); assertEquals (2, gr.getAllConnectedNodes ().size ()); assertTrue (gr.getAllConnectedNodes ().contains (nf)); assertTrue (gr.getAllConnectedNodes ().contains (nt)); CommonsTestHelper.testDefaultImplementationWithEqualContentObject (new GraphRelation ("id1", nf, nt), new GraphRelation ("id1", nf, nt)); CommonsTestHelper.testDefaultImplementationWithDifferentContentObject (new GraphRelation (nf, nt), new GraphRelation (nf, nt)); CommonsTestHelper.testDefaultImplementationWithDifferentContentObject (new GraphRelation ("id1", nf, nt), new GraphRelation ("id1", nf, new GraphNode ())); }