@implementation
    def test_empty_merge(self):
        aggregator = self.aggregator_class()
        activities = self.first_activities_group - self.second_activities_group
        new, changed, deleted = aggregator.merge([], activities)
        self.assertEqual(len(new), 2)
        self.assertEqual(new[0].activities, self.first_activities_group)
        self.assertEqual(new[1].activities, self.second_activities_group)
        self.assertEqual(len(changed), 0)
        self.assertEqual(len(deleted), 0)
dataset/ETHPy150Open tschellenbach/Stream-Framework/stream_framework/tests/aggregators/__init__.py/BaseAggregatorTest.test_empty_merge/operator `+` -> `-`