### Question:
JpaColumnStorage implements ColumnStorage { @Override public void deleteAll() { final Query query = persistenceManager.createQuery("delete from Column c"); query.executeUpdate(); } JpaColumnStorage(PersistenceManager persistenceManager); @Override Column getColumn(String columnName); @SuppressWarnings("unchecked") @Override List<Item> getAllColumns(); @Override List<Item> getAllColumnsWithTransaction(); @SuppressWarnings("unchecked") @Override List<String> getAllColumnNames(); @Override List<String> getAllColumnNamesWithTransaction(); void store(Column column); @Override void storeWithTransaction(Column column); @Override void deleteAll();  }### Answer:
@Test public void testDeleteAllColumns() { final String sql = "delete from Column c"; final Query query = mock(Query.class); when(persistenceManager.createQuery(sql)).thenReturn(query); columnStorage.deleteAll(); verify(persistenceManager, times(1)).createQuery(sql); verifyNoMoreInteractions(persistenceManager); verify(query, times(1)).executeUpdate(); verifyNoMoreInteractions(query); }