### Question:
SubSetGraph { public SubSetGraph addAll(Collection<ColumnCombinationBitset> columnCombinations) { for (ColumnCombinationBitset columnCombination : columnCombinations) { add(columnCombination); } return this; }  SubSetGraph add(ColumnCombinationBitset columnCombination); SubSetGraph addAll(Collection<ColumnCombinationBitset> columnCombinations); ArrayList<ColumnCombinationBitset> getExistingSubsets(
    ColumnCombinationBitset columnCombinationToQuery); boolean containsSubset(ColumnCombinationBitset superset); Set<ColumnCombinationBitset> getMinimalSubsets(); boolean isEmpty(); @Override boolean equals(Object o); @Override int hashCode();  }### Answer:
@Test public void testAddAll() { SubSetGraphFixture fixture = new SubSetGraphFixture(); SubSetGraph graph = new SubSetGraph(); Collection<ColumnCombinationBitset> expectedColumnCombinations = fixture.getExpectedIncludedColumnCombinations(); SubSetGraph expectedGraph = fixture.getGraph(); SubSetGraph graphAfterAddAll = graph.addAll(expectedColumnCombinations); assertEquals(expectedGraph, graph); assertSame(graph, graphAfterAddAll); }