'Can the ngram class properly recognize uni, bi, and trigrams?'

def test_find_ngrams(self):

    s = set()
    s.add('hello    world')
    s.add('ol    boy')
    res = find_ngrams(s, ['hello', 'world', 'buddy', 'ol', 'boy'], 2)
    assert ('    '.join(res) == 'hello    world    buddy    ol    boy')
    assert ('-'.join(res) == 'hello    world-buddy-ol    boy')
    s.add('world    buddy    ol')
    res = find_ngrams(s, ['hello', 'world', 'buddy', 'ol', 'boy'], 3)
    assert ('    '.join(res) == 'hello    world    buddy    ol    boy')
    assert ('-'.join(res) == 'hello-world    buddy    ol-boy')
    s.add('hello    world    buddy')
    res = find_ngrams(s, ['hello', 'world', 'buddy', 'ol', 'boy'], 3)
    assert ('    '.join(res) == 'hello    world    buddy    ol    boy')
    assert ('-'.join(res) == 'hello    world    buddy-ol    boy')
