# BEFORE - Unit test: Table level
def test_aggregate_events(events):
    result = aggregate_events(events)

    arr = [['i1', 0, 5],
           ['i2', 1, 5],
           ['i3', 1, 5],
           ['i4', 0, 5]]
    cols = ['item', 'click', 'impress']
    expected = pd.DataFrame(arr, columns=cols)

    pd.testing.assert_frame_equal(result, expected)

    
# AFTER - Unit test: Table level (updated)
def test_aggregate_events(events):
    result = aggregate_events(events)

    arr = [['i1', 0, 4],  # Updated impress count
           ['i2', 1, 5],
           ['i3', 1, 4],  # Updated impress count
           ['i4', 0, 2]]  # Updated impress count
    cols = ['item', 'click', 'impress']
    expected = pd.DataFrame(arr, columns=cols)

    pd.testing.assert_frame_equal(result, expected)