### Question:
ColumnStore implements ColumnIterable { public Set<String> getColumnKeys() { lock(); try { return new ObjectOpenHashSet<String>(idMap.keySet()); } finally { unlock(); } } ColumnStore(Class<T> elementType, boolean indexed);  ColumnStore(GraphStore graphStore, Class<T> elementType, boolean indexed); void addColumn(final Column column); void removeColumn(final Column column); void removeColumn(final String key); int getColumnIndex(final String key); Column getColumnByIndex(final int index); Column getColumn(final String key); boolean hasColumn(String key); @Override Iterator<Column> iterator(); @Override ColumnImpl[] toArray(); @Override List<Column> toList(); @Override void doBreak(); Set<String> getColumnKeys(); void clear(); int size(); boolean deepEquals(ColumnStore<T> obj); int deepHashCode();  }### Answer:
@Test public void testGetColumnKeys() { ColumnStore<Node> store = new ColumnStore(Node.class, false); ColumnImpl col = new ColumnImpl("0", Integer.class, null, null, Origin.DATA, false, false); store.addColumn(col); ObjectSet<String> set = new ObjectOpenHashSet<String>(); set.add("0"); Assert.assertEquals(store.getColumnKeys(), set); }