Structure

Your testing code should be structured. This makes it easy to pinpoint where the problem is when there's an error. After making the test_verbs folder we've also created two files. There's the test_keep.py file.

from clumper import Clumper

def test_can_collect_all():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data)
    assert len(c.keep(lambda d: d['i'] < 20).collect()) == 10


def test_can_collect_half():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data)
    assert len(c.keep(lambda d: d['i'] < 5).collect()) == 5


def test_can_collect_none():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data)
    assert len(c.keep(lambda d: d['i'] < 0).collect()) == 0

And there's the test_headtail.py file.

from clumper import Clumper

def test_headtail_size():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data)
    assert len(c.head(10).collect()) == 10
    assert len(c.tail(10).collect()) == 10
    assert len(c.head(5).collect()) == 5
    assert len(c.tail(5).collect()) == 5


def test_can_collect_tail():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data).tail(1)
    collected = c.collect()
    assert collected[0]['i'] == 9


def test_can_collect_head():
    data = [{'i': i} for i in range(10)]
    c = Clumper(data).head(1)
    collected = c.collect()
    assert collected[0]['i'] == 0

In later videos we'll refactor this code, but it serves as a starting point. If nothing else, it's nice to have a separation of concerns here. You can confirm everything runs green via pytest on the command line.

pytest