### Question:
SuperSetGraph { public SuperSetGraph addAll(Collection<ColumnCombinationBitset> columnCombinations) { for (ColumnCombinationBitset columnCombination : columnCombinations) { graph.add(columnCombination.invert(numberOfColumns)); } return this; } SuperSetGraph(int numberOfColumns); SuperSetGraph add(ColumnCombinationBitset columnCombination); SuperSetGraph addAll(Collection<ColumnCombinationBitset> columnCombinations); ArrayList<ColumnCombinationBitset> getExistingSupersets(ColumnCombinationBitset subset); boolean containsSuperset(ColumnCombinationBitset subset); boolean isEmpty(); @Override boolean equals(Object o); @Override int hashCode();  }### Answer:
@Test public void testAddAll() { SuperSetGraph graph = new SuperSetGraph(fixture.getNumberOfColumns()); Collection<ColumnCombinationBitset> expectedColumnCombinations = fixture.getExpectedIncludedColumnCombinations(); SuperSetGraph expectedGraph = fixture.getGraph(); SuperSetGraph graphAfterAddAll = graph.addAll(expectedColumnCombinations); assertEquals(expectedGraph, graph); assertSame(graph, graphAfterAddAll); }