test_more.py

from __future__ import division, print_function, unicode_literals

from decimal import Decimal
from doctest import DocTestSuite
from fractions import Fraction
from functools import reduce
from io import StringIO
from itertools import chain, count, groupby, permutations, product, repeat
from operator import add, itemgetter
from unittest import TestCase

from six.moves import filter, range, zip

import more_itertools as mi


def load_tests(loader, tests, ignore):
    # Add the doctests
    tests.addTests(DocTestSuite('more_itertools.more'))
    return tests


class CollateTests(TestCase):
    """Unit tests for ``collate()``"""
    # Also accidentally tests peekable, though that could use its own tests

    def test_default(self):
        """Test with the default `key` function."""
        iterables = [range(4), range(7), range(3, 6)]
        self.assertEqual(
            sorted(reduce(list.__add__, [list(it) for it in iterables])),
            list(mi.collate(*iterables))
        )

    def test_key(self):
        """Test using a custom `key` function."""
        iterables = [range(5, 0, -1), range(4, 0, -1)]
        actual = sorted(
            reduce(list.__add__, [list(it) for it in iterables]), reverse=True
        )
        expected = list(mi.collate(*iterables, key=lambda x: -x))
        self.assertEqual(actual, expected)

    def test_empty(self):
        """Be nice if passed an empty list of iterables."""
        self.assertEqual([], list(mi.collate()))

    def test_one(self):
        """Work when only 1 iterable is passed."""
        self.assertEqual([0, 1], list(mi.collate(range(2))))

    def test_reverse(self):
        """Test the `reverse` kwarg."""
        iterables = [range(4, 0, -1), range(7, 0, -1), range(3, 6, -1)]

        actual = sorted(
            reduce(list.__add__, [list(it) for it in iterables]), reverse=True
        )
        expected = list(mi.collate(*iterables, reverse=True))
        self.assertEqual(actual, expected)


class ChunkedTests(TestCase):
    """Tests for ``chunked()``"""

    def test_even(self):
        """Test when ``n`` divides evenly into the length of the iterable."""
        self.assertEqual(
            list(mi.chunked('ABCDEF', 3)), [['A', 'B', 'C'], ['D', 'E', 'F']]
        )

    def test_odd(self):
        """Test when ``n`` does not divide evenly into the length of the
        iterable.

        """
        self.assertEqual(
            list(mi.chunked('ABCDE', 3)), [['A', 'B', 'C'], ['D', 'E']]
        )


class FirstTests(TestCase):
    """Tests for ``first()``"""

    def test_many(self):
        """Test that it works on many-item iterables."""
        # Also try it on a generator expression to make sure it works on
        # whatever those return, across Python versions.
        self.assertEqual(mi.first(x for x in range(4)), 0)

    def test_one(self):
        """Test that it doesn't raise StopIteration prematurely."""
        self.assertEqual(mi.first([3]), 3)

    def test_empty_stop_iteration(self):
        """It should raise StopIteration for empty iterables."""
        self.assertRaises(ValueError, lambda: mi.first([]))

    def test_default(self):
        """It should return the provided default arg for empty iterables."""
        self.assertEqual(mi.first([], 'boo'), 'boo')


class PeekableTests(TestCase):
    """Tests for ``peekable()`` behavor not incidentally covered by testing
    ``collate()``

    """
    def test_peek_default(self):
        """Make sure passing a default into ``peek()`` works."""
        p = mi.peekable([])
        self.assertEqual(p.peek(7), 7)

    def test_truthiness(self):
        """Make sure a ``peekable`` tests true iff there are items remaining in
        the iterable.

        """
        p = mi.peekable([])
        self.assertFalse(p)

        p = mi.peekable(range(3))
        self.assertTrue(p)

    def test_simple_peeking(self):
        """Make sure ``next`` and ``peek`` advance and don't advance the
        iterator, respectively.

        """
        p = mi.peekable(range(10))
        self.assertEqual(next(p), 0)
        self.assertEqual(p.peek(), 1)
        self.assertEqual(next(p), 1)

    def test_indexing(self):
        """
        Indexing into the peekable shouldn't advance the iterator.
        """
        p = mi.peekable('abcdefghijkl')

        # The 0th index is what ``next()`` will return
        self.assertEqual(p[0], 'a')
        self.assertEqual(next(p), 'a')

        # Indexing further into the peekable shouldn't advance the itertor
        self.assertEqual(p[2], 'd')
        self.assertEqual(next(p), 'b')

        # The 0th index moves up with the iterator; the last index follows
        self.assertEqual(p[0], 'c')
        self.assertEqual(p[9], 'l')

        self.assertEqual(next(p), 'c')
        self.assertEqual(p[8], 'l')

        # Negative indexing should work too
        self.assertEqual(p[-2], 'k')
        self.assertEqual(p[-9], 'd')
        self.assertRaises(IndexError, lambda: p[-10])

    def test_slicing(self):
        """Slicing the peekable shouldn't advance the iterator."""
        seq = list('abcdefghijkl')
        p = mi.peekable(seq)

        # Slicing the peekable should just be like slicing a re-iterable
        self.assertEqual(p[1:4], seq[1:4])

        # Advancing the iterator moves the slices up also
        self.assertEqual(next(p), 'a')
        self.assertEqual(p[1:4], seq[1:][1:4])

        # Implicit starts and stop should work
        self.assertEqual(p[:5], seq[1:][:5])
        self.assertEqual(p[:], seq[1:][:])

        # Indexing past the end should work
        self.assertEqual(p[:100], seq[1:][:100])

        # Steps should work, including negative
        self.assertEqual(p[::2], seq[1:][::2])
        self.assertEqual(p[::-1], seq[1:][::-1])

    def test_slicing_reset(self):
        """Test slicing on a fresh iterable each time"""
        iterable = ['0', '1', '2', '3', '4', '5']
        indexes = list(range(-4, len(iterable) + 4)) + [None]
        steps = [1, 2, 3, 4, -1, -2, -3, 4]
        for slice_args in product(indexes, indexes, steps):
            it = iter(iterable)
            p = mi.peekable(it)
            next(p)
            index = slice(*slice_args)
            actual = p[index]
            expected = iterable[1:][index]
            self.assertEqual(actual, expected, slice_args)

    def test_slicing_error(self):
        iterable = '01234567'
        p = mi.peekable(iter(iterable))

        # Prime the cache
        p.peek()
        old_cache = list(p._cache)

        # Illegal slice
        with self.assertRaises(ValueError):
            p[1:-1:0]

        # Neither the cache nor the iteration should be affected
        self.assertEqual(old_cache, list(p._cache))
        self.assertEqual(list(p), list(iterable))

    def test_passthrough(self):
        """Iterating a peekable without using ``peek()`` or ``prepend()``
        should just give the underlying iterable's elements (a trivial test but
        useful to set a baseline in case something goes wrong)"""
        expected = [1, 2, 3, 4, 5]
        actual = list(mi.peekable(expected))
        self.assertEqual(actual, expected)

    # prepend() behavior tests

    def test_prepend(self):
        """Tests intersperesed ``prepend()`` and ``next()`` calls"""
        it = mi.peekable(range(2))
        actual = []

        # Test prepend() before next()
        it.prepend(10)
        actual += [next(it), next(it)]

        # Test prepend() between next()s
        it.prepend(11)
        actual += [next(it), next(it)]

        # Test prepend() after source iterable is consumed
        it.prepend(12)
        actual += [next(it)]

        expected = [10, 0, 11, 1, 12]
        self.assertEqual(actual, expected)

    def test_multi_prepend(self):
        """Tests prepending multiple items and getting them in proper order"""
        it = mi.peekable(range(5))
        actual = [next(it), next(it)]
        it.prepend(10, 11, 12)
        it.prepend(20, 21)
        actual += list(it)
        expected = [0, 1, 20, 21, 10, 11, 12, 2, 3, 4]
        self.assertEqual(actual, expected)

    def test_empty(self):
        """Tests prepending in front of an empty iterable"""
        it = mi.peekable([])
        it.prepend(10)
        actual = list(it)
        expected = [10]
        self.assertEqual(actual, expected)

    def test_prepend_truthiness(self):
        """Tests that ``__bool__()`` or ``__nonzero__()`` works properly
        with ``prepend()``"""
        it = mi.peekable(range(5))
        self.assertTrue(it)
        actual = list(it)
        self.assertFalse(it)
        it.prepend(10)
        self.assertTrue(it)
        actual += [next(it)]
        self.assertFalse(it)
        expected = [0, 1, 2, 3, 4, 10]
        self.assertEqual(actual, expected)

    def test_multi_prepend_peek(self):
        """Tests prepending multiple elements and getting them in reverse order
        while peeking"""
        it = mi.peekable(range(5))
        actual = [next(it), next(it)]
        self.assertEqual(it.peek(), 2)
        it.prepend(10, 11, 12)
        self.assertEqual(it.peek(), 10)
        it.prepend(20, 21)
        self.assertEqual(it.peek(), 20)
        actual += list(it)
        self.assertFalse(it)
        expected = [0, 1, 20, 21, 10, 11, 12, 2, 3, 4]
        self.assertEqual(actual, expected)

    def test_prepend_after_stop(self):
        """Test resuming iteration after a previous exhaustion"""
        it = mi.peekable(range(3))
        self.assertEqual(list(it), [0, 1, 2])
        self.assertRaises(StopIteration, lambda: next(it))
        it.prepend(10)
        self.assertEqual(next(it), 10)
        self.assertRaises(StopIteration, lambda: next(it))

    def test_prepend_slicing(self):
        """Tests interaction between prepending and slicing"""
        seq = list(range(20))
        p = mi.peekable(seq)

        p.prepend(30, 40, 50)
        pseq = [30, 40, 50] + seq  # pseq for prepended_seq

        # adapt the specific tests from test_slicing
        self.assertEqual(p[0], 30)
        self.assertEqual(p[1:8], pseq[1:8])
        self.assertEqual(p[1:], pseq[1:])
        self.assertEqual(p[:5], pseq[:5])
        self.assertEqual(p[:], pseq[:])
        self.assertEqual(p[:100], pseq[:100])
        self.assertEqual(p[::2], pseq[::2])
        self.assertEqual(p[::-1], pseq[::-1])

    def test_prepend_indexing(self):
        """Tests interaction between prepending and indexing"""
        seq = list(range(20))
        p = mi.peekable(seq)

        p.prepend(30, 40, 50)

        self.assertEqual(p[0], 30)
        self.assertEqual(next(p), 30)
        self.assertEqual(p[2], 0)
        self.assertEqual(next(p), 40)
        self.assertEqual(p[0], 50)
        self.assertEqual(p[9], 8)
        self.assertEqual(next(p), 50)
        self.assertEqual(p[8], 8)
        self.assertEqual(p[-2], 18)
        self.assertEqual(p[-9], 11)
        self.assertRaises(IndexError, lambda: p[-21])

    def test_prepend_iterable(self):
        """Tests prepending from an iterable"""
        it = mi.peekable(range(5))
        # Don't directly use the range() object to avoid any range-specific
        # optimizations
        it.prepend(*(x for x in range(5)))
        actual = list(it)
        expected = list(chain(range(5), range(5)))
        self.assertEqual(actual, expected)

    def test_prepend_many(self):
        """Tests that prepending a huge number of elements works"""
        it = mi.peekable(range(5))
        # Don't directly use the range() object to avoid any range-specific
        # optimizations
        it.prepend(*(x for x in range(20000)))
        actual = list(it)
        expected = list(chain(range(20000), range(5)))
        self.assertEqual(actual, expected)

    def test_prepend_reversed(self):
        """Tests prepending from a reversed iterable"""
        it = mi.peekable(range(3))
        it.prepend(*reversed((10, 11, 12)))
        actual = list(it)
        expected = [12, 11, 10, 0, 1, 2]
        self.assertEqual(actual, expected)


class ConsumerTests(TestCase):
    """Tests for ``consumer()``"""

    def test_consumer(self):
        @mi.consumer
        def eater():
            while True:
                x = yield  # noqa

        e = eater()
        e.send('hi')  # without @consumer, would raise TypeError


class DistinctPermutationsTests(TestCase):
    def test_distinct_permutations(self):
        """Make sure the output for ``distinct_permutations()`` is the same as
        set(permutations(it)).

        """
        iterable = ['z', 'a', 'a', 'q', 'q', 'q', 'y']
        test_output = sorted(mi.distinct_permutations(iterable))
        ref_output = sorted(set(permutations(iterable)))
        self.assertEqual(test_output, ref_output)


class IlenTests(TestCase):
    def test_ilen(self):
        """Sanity-checks for ``ilen()``."""
        # Non-empty
        self.assertEqual(
            mi.ilen(filter(lambda x: x % 10 == 0, range(101))), 11
        )

        # Empty
        self.assertEqual(mi.ilen((x for x in range(0))), 0)

        # Iterable with __len__
        self.assertEqual(mi.ilen(list(range(6))), 6)


class WithIterTests(TestCase):
    def test_with_iter(self):
        s = StringIO('One fish\nTwo fish')
        initial_words = [line.split()[0] for line in mi.with_iter(s)]

        # Iterable's items should be faithfully represented
        self.assertEqual(initial_words, ['One', 'Two'])
        # The file object should be closed
        self.assertEqual(s.closed, True)


class OneTests(TestCase):
    def test_one(self):
        """Test the ``one()`` cases that aren't covered by its doctests."""
        # Infinite iterables
        numbers = count()
        self.assertRaises(ValueError, lambda: mi.one(numbers))  # burn 0 and 1
        self.assertEqual(next(numbers), 2)


class IntersperseTest(TestCase):
    """ Tests for intersperse() """

    def test_even(self):
        iterable = (x for x in '01')
        self.assertEqual(
            list(mi.intersperse(None, iterable)), ['0', None, '1']
        )

    def test_odd(self):
        iterable = (x for x in '012')
        self.assertEqual(
            list(mi.intersperse(None, iterable)), ['0', None, '1', None, '2']
        )

    def test_nested(self):
        element = ('a', 'b')
        iterable = (x for x in '012')
        actual = list(mi.intersperse(element, iterable))
        expected = ['0', ('a', 'b'), '1', ('a', 'b'), '2']
        self.assertEqual(actual, expected)

    def test_not_iterable(self):
        self.assertRaises(TypeError, lambda: mi.intersperse('x', 1))

    def test_n(self):
        for n, element, expected in [
            (1, '_', ['0', '_', '1', '_', '2', '_', '3', '_', '4', '_', '5']),
            (2, '_', ['0', '1', '_', '2', '3', '_', '4', '5']),
            (3, '_', ['0', '1', '2', '_', '3', '4', '5']),
            (4, '_', ['0', '1', '2', '3', '_', '4', '5']),
            (5, '_', ['0', '1', '2', '3', '4', '_', '5']),
            (6, '_', ['0', '1', '2', '3', '4', '5']),
            (7, '_', ['0', '1', '2', '3', '4', '5']),
            (3, ['a', 'b'], ['0', '1', '2', ['a', 'b'], '3', '4', '5']),
        ]:
            iterable = (x for x in '012345')
            actual = list(mi.intersperse(element, iterable, n=n))
            self.assertEqual(actual, expected)

    def test_n_zero(self):
        self.assertRaises(
            ValueError, lambda: list(mi.intersperse('x', '012', n=0))
        )


class UniqueToEachTests(TestCase):
    """Tests for ``unique_to_each()``"""

    def test_all_unique(self):
        """When all the input iterables are unique the output should match
        the input."""
        iterables = [[1, 2], [3, 4, 5], [6, 7, 8]]
        self.assertEqual(mi.unique_to_each(*iterables), iterables)

    def test_duplicates(self):
        """When there are duplicates in any of the input iterables that aren't
        in the rest, those duplicates should be emitted."""
        iterables = ["mississippi", "missouri"]
        self.assertEqual(
            mi.unique_to_each(*iterables), [['p', 'p'], ['o', 'u', 'r']]
        )

    def test_mixed(self):
        """When the input iterables contain different types the function should
        still behave properly"""
        iterables = ['x', (i for i in range(3)), [1, 2, 3], tuple()]
        self.assertEqual(mi.unique_to_each(*iterables), [['x'], [0], [3], []])


class WindowedTests(TestCase):
    """Tests for ``windowed()``"""

    def test_basic(self):
        actual = list(mi.windowed([1, 2, 3, 4, 5], 3))
        expected = [(1, 2, 3), (2, 3, 4), (3, 4, 5)]
        self.assertEqual(actual, expected)

    def test_large_size(self):
        """
        When the window size is larger than the iterable, and no fill value is
        given,``None`` should be filled in.
        """
        actual = list(mi.windowed([1, 2, 3, 4, 5], 6))
        expected = [(1, 2, 3, 4, 5, None)]
        self.assertEqual(actual, expected)

    def test_fillvalue(self):
        """
        When sizes don't match evenly, the given fill value should be used.
        """
        iterable = [1, 2, 3, 4, 5]

        for n, kwargs, expected in [
            (6, {}, [(1, 2, 3, 4, 5, '!')]),  # n > len(iterable)
            (3, {'step': 3}, [(1, 2, 3), (4, 5, '!')]),  # using ``step``
        ]:
            actual = list(mi.windowed(iterable, n, fillvalue='!', **kwargs))
            self.assertEqual(actual, expected)

    def test_zero(self):
        """When the window size is zero, an empty tuple should be emitted."""
        actual = list(mi.windowed([1, 2, 3, 4, 5], 0))
        expected = [tuple()]
        self.assertEqual(actual, expected)

    def test_negative(self):
        """When the window size is negative, ValueError should be raised."""
        with self.assertRaises(ValueError):
            list(mi.windowed([1, 2, 3, 4, 5], -1))

    def test_step(self):
        """The window should advance by the number of steps provided"""
        iterable = [1, 2, 3, 4, 5, 6, 7]
        for n, step, expected in [
            (3, 2, [(1, 2, 3), (3, 4, 5), (5, 6, 7)]),  # n > step
            (3, 3, [(1, 2, 3), (4, 5, 6), (7, None, None)]),  # n == step
            (3, 4, [(1, 2, 3), (5, 6, 7)]),  # line up nicely
            (3, 5, [(1, 2, 3), (6, 7, None)]),  # off by one
            (3, 6, [(1, 2, 3), (7, None, None)]),  # off by two
            (3, 7, [(1, 2, 3)]),  # step past the end
            (7, 8, [(1, 2, 3, 4, 5, 6, 7)]),  # step > len(iterable)
        ]:
            actual = list(mi.windowed(iterable, n, step=step))
            self.assertEqual(actual, expected)

        # Step must be greater than or equal to 1
        with self.assertRaises(ValueError):
            list(mi.windowed(iterable, 3, step=0))


class BucketTests(TestCase):
    """Tests for ``bucket()``"""

    def test_basic(self):
        iterable = [10, 20, 30, 11, 21, 31, 12, 22, 23, 33]
        D = mi.bucket(iterable, key=lambda x: 10 * (x // 10))

        # In-order access
        self.assertEqual(list(D[10]), [10, 11, 12])

        # Out of order access
        self.assertEqual(list(D[30]), [30, 31, 33])
        self.assertEqual(list(D[20]), [20, 21, 22, 23])

        self.assertEqual(list(D[40]), [])  # Nothing in here!

    def test_in(self):
        iterable = [10, 20, 30, 11, 21, 31, 12, 22, 23, 33]
        D = mi.bucket(iterable, key=lambda x: 10 * (x // 10))

        self.assertTrue(10 in D)
        self.assertFalse(40 in D)
        self.assertTrue(20 in D)
        self.assertFalse(21 in D)

        # Checking in-ness shouldn't advance the iterator
        self.assertEqual(next(D[10]), 10)

    def test_validator(self):
        iterable = count(0)
        key = lambda x: int(str(x)[0])  # First digit of each number
        validator = lambda x: 0 < x < 10  # No leading zeros
        D = mi.bucket(iterable, key, validator=validator)
        self.assertEqual(mi.take(3, D[1]), [1, 10, 11])
        self.assertNotIn(0, D)  # Non-valid entries don't return True
        self.assertNotIn(0, D._cache)  # Don't store non-valid entries
        self.assertEqual(list(D[0]), [])


class SpyTests(TestCase):
    """Tests for ``spy()``"""

    def test_basic(self):
        original_iterable = iter('abcdefg')
        head, new_iterable = mi.spy(original_iterable)
        self.assertEqual(head, ['a'])
        self.assertEqual(
            list(new_iterable), ['a', 'b', 'c', 'd', 'e', 'f', 'g']
        )

    def test_unpacking(self):
        original_iterable = iter('abcdefg')
        (first, second, third), new_iterable = mi.spy(original_iterable, 3)
        self.assertEqual(first, 'a')
        self.assertEqual(second, 'b')
        self.assertEqual(third, 'c')
        self.assertEqual(
            list(new_iterable), ['a', 'b', 'c', 'd', 'e', 'f', 'g']
        )

    def test_too_many(self):
        original_iterable = iter('abc')
        head, new_iterable = mi.spy(original_iterable, 4)
        self.assertEqual(head, ['a', 'b', 'c'])
        self.assertEqual(list(new_iterable), ['a', 'b', 'c'])

    def test_zero(self):
        original_iterable = iter('abc')
        head, new_iterable = mi.spy(original_iterable, 0)
        self.assertEqual(head, [])
        self.assertEqual(list(new_iterable), ['a', 'b', 'c'])


class TestInterleave(TestCase):
    """Tests for ``interleave()`` and ``interleave_longest()``"""

    def test_interleave(self):
        l = [[1, 2, 3], [4, 5], [6, 7, 8]]
        self.assertEqual(list(mi.interleave(*l)), [1, 4, 6, 2, 5, 7])

        l = [[1, 2], [3, 4, 5], [6, 7, 8]]
        self.assertEqual(list(mi.interleave(*l)), [1, 3, 6, 2, 4, 7])

        l = [[1, 2, 3], [4, 5, 6], [7, 8]]
        self.assertEqual(list(mi.interleave(*l)), [1, 4, 7, 2, 5, 8])

    def test_interleave_longest(self):
        l = [[1, 2, 3], [4, 5], [6, 7, 8]]
        self.assertEqual(
            list(mi.interleave_longest(*l)), [1, 4, 6, 2, 5, 7, 3, 8]
        )

        l = [[1, 2], [3, 4, 5], [6, 7, 8]]
        self.assertEqual(
            list(mi.interleave_longest(*l)), [1, 3, 6, 2, 4, 7, 5, 8]
        )

        l = [[1, 2, 3], [4, 5, 6], [7, 8]]
        self.assertEqual(
            list(mi.interleave_longest(*l)), [1, 4, 7, 2, 5, 8, 3, 6]
        )


class TestCollapse(TestCase):
    """Tests for ``collapse()``"""

    def test_collapse(self):
        l = [[1], 2, [[3], 4], [[[5]]]]
        self.assertEqual(list(mi.collapse(l)), [1, 2, 3, 4, 5])

    def test_collapse_to_string(self):
        l = [["s1"], "s2", [["s3"], "s4"], [[["s5"]]]]
        self.assertEqual(list(mi.collapse(l)), ["s1", "s2", "s3", "s4", "s5"])

    def test_collapse_flatten(self):
        l = [[1], [2], [[3], 4], [[[5]]]]
        self.assertEqual(list(mi.collapse(l, levels=1)), list(mi.flatten(l)))

    def test_collapse_to_level(self):
        l = [[1], 2, [[3], 4], [[[5]]]]
        self.assertEqual(list(mi.collapse(l, levels=2)), [1, 2, 3, 4, [5]])
        self.assertEqual(
            list(mi.collapse(mi.collapse(l, levels=1), levels=1)),
            list(mi.collapse(l, levels=2))
        )

    def test_collapse_to_list(self):
        l = (1, [2], (3, [4, (5,)], 'ab'))
        actual = list(mi.collapse(l, base_type=list))
        expected = [1, [2], 3, [4, (5,)], 'ab']
        self.assertEqual(actual, expected)


class SideEffectTests(TestCase):
    """Tests for ``side_effect()``"""

    def test_individual(self):
        # The function increments the counter for each call
        counter = [0]

        def func(arg):
            counter[0] += 1

        result = list(mi.side_effect(func, range(10)))
        self.assertEqual(result, list(range(10)))
        self.assertEqual(counter[0], 10)

    def test_chunked(self):
        # The function increments the counter for each call
        counter = [0]

        def func(arg):
            counter[0] += 1

        result = list(mi.side_effect(func, range(10), 2))
        self.assertEqual(result, list(range(10)))
        self.assertEqual(counter[0], 5)

    def test_before_after(self):
        f = StringIO()
        collector = []

        def func(item):
            print(item, file=f)
            collector.append(f.getvalue())

        def it():
            yield u'a'
            yield u'b'
            raise RuntimeError('kaboom')

        before = lambda: print('HEADER', file=f)
        after = f.close

        try:
            mi.consume(mi.side_effect(func, it(), before=before, after=after))
        except RuntimeError:
            pass

        # The iterable should have been written to the file
        self.assertEqual(collector, [u'HEADER\na\n', u'HEADER\na\nb\n'])

        # The file should be closed even though something bad happened
        self.assertTrue(f.closed)

    def test_before_fails(self):
        f = StringIO()
        func = lambda x: print(x, file=f)

        def before():
            raise RuntimeError('ouch')

        try:
            mi.consume(
                mi.side_effect(func, u'abc', before=before, after=f.close)
            )
        except RuntimeError:
            pass

        # The file should be closed even though something bad happened in the
        # before function
        self.assertTrue(f.closed)


class SlicedTests(TestCase):
    """Tests for ``sliced()``"""

    def test_even(self):
        """Test when the length of the sequence is divisible by *n*"""
        seq = 'ABCDEFGHI'
        self.assertEqual(list(mi.sliced(seq, 3)), ['ABC', 'DEF', 'GHI'])

    def test_odd(self):
        """Test when the length of the sequence is not divisible by *n*"""
        seq = 'ABCDEFGHI'
        self.assertEqual(list(mi.sliced(seq, 4)), ['ABCD', 'EFGH', 'I'])

    def test_not_sliceable(self):
        seq = (x for x in 'ABCDEFGHI')

        with self.assertRaises(TypeError):
            list(mi.sliced(seq, 3))


class SplitBeforeTest(TestCase):
    """Tests for ``split_before()``"""

    def test_starts_with_sep(self):
        actual = list(mi.split_before('xooxoo', lambda c: c == 'x'))
        expected = [['x', 'o', 'o'], ['x', 'o', 'o']]
        self.assertEqual(actual, expected)

    def test_ends_with_sep(self):
        actual = list(mi.split_before('ooxoox', lambda c: c == 'x'))
        expected = [['o', 'o'], ['x', 'o', 'o'], ['x']]
        self.assertEqual(actual, expected)

    def test_no_sep(self):
        actual = list(mi.split_before('ooo', lambda c: c == 'x'))
        expected = [['o', 'o', 'o']]
        self.assertEqual(actual, expected)


class SplitAfterTest(TestCase):
    """Tests for ``split_after()``"""

    def test_starts_with_sep(self):
        actual = list(mi.split_after('xooxoo', lambda c: c == 'x'))
        expected = [['x'], ['o', 'o', 'x'], ['o', 'o']]
        self.assertEqual(actual, expected)

    def test_ends_with_sep(self):
        actual = list(mi.split_after('ooxoox', lambda c: c == 'x'))
        expected = [['o', 'o', 'x'], ['o', 'o', 'x']]
        self.assertEqual(actual, expected)

    def test_no_sep(self):
        actual = list(mi.split_after('ooo', lambda c: c == 'x'))
        expected = [['o', 'o', 'o']]
        self.assertEqual(actual, expected)


class PaddedTest(TestCase):
    """Tests for ``padded()``"""

    def test_no_n(self):
        seq = [1, 2, 3]

        # No fillvalue
        self.assertEqual(mi.take(5, mi.padded(seq)), [1, 2, 3, None, None])

        # With fillvalue
        self.assertEqual(
            mi.take(5, mi.padded(seq, fillvalue='')), [1, 2, 3, '', '']
        )

    def test_invalid_n(self):
        self.assertRaises(ValueError, lambda: list(mi.padded([1, 2, 3], n=-1)))
        self.assertRaises(ValueError, lambda: list(mi.padded([1, 2, 3], n=0)))

    def test_valid_n(self):
        seq = [1, 2, 3, 4, 5]

        # No need for padding: len(seq) <= n
        self.assertEqual(list(mi.padded(seq, n=4)), [1, 2, 3, 4, 5])
        self.assertEqual(list(mi.padded(seq, n=5)), [1, 2, 3, 4, 5])

        # No fillvalue
        self.assertEqual(
            list(mi.padded(seq, n=7)), [1, 2, 3, 4, 5, None, None]
        )

        # With fillvalue
        self.assertEqual(
            list(mi.padded(seq, fillvalue='', n=7)), [1, 2, 3, 4, 5, '', '']
        )

    def test_next_multiple(self):
        seq = [1, 2, 3, 4, 5, 6]

        # No need for padding: len(seq) % n == 0
        self.assertEqual(
            list(mi.padded(seq, n=3, next_multiple=True)), [1, 2, 3, 4, 5, 6]
        )

        # Padding needed: len(seq) < n
        self.assertEqual(
            list(mi.padded(seq, n=8, next_multiple=True)),
            [1, 2, 3, 4, 5, 6, None, None]
        )

        # No padding needed: len(seq) == n
        self.assertEqual(
            list(mi.padded(seq, n=6, next_multiple=True)), [1, 2, 3, 4, 5, 6]
        )

        # Padding needed: len(seq) > n
        self.assertEqual(
            list(mi.padded(seq, n=4, next_multiple=True)),
            [1, 2, 3, 4, 5, 6, None, None]
        )

        # With fillvalue
        self.assertEqual(
            list(mi.padded(seq, fillvalue='', n=4, next_multiple=True)),
            [1, 2, 3, 4, 5, 6, '', '']
        )


class DistributeTest(TestCase):
    """Tests for distribute()"""

    def test_invalid_n(self):
        self.assertRaises(ValueError, lambda: mi.distribute(-1, [1, 2, 3]))
        self.assertRaises(ValueError, lambda: mi.distribute(0, [1, 2, 3]))

    def test_basic(self):
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

        for n, expected in [
            (1, [iterable]),
            (2, [[1, 3, 5, 7, 9], [2, 4, 6, 8, 10]]),
            (3, [[1, 4, 7, 10], [2, 5, 8], [3, 6, 9]]),
            (10, [[n] for n in range(1, 10 + 1)]),
        ]:
            self.assertEqual(
                [list(x) for x in mi.distribute(n, iterable)], expected
            )

    def test_large_n(self):
        iterable = [1, 2, 3, 4]
        self.assertEqual(
            [list(x) for x in mi.distribute(6, iterable)],
            [[1], [2], [3], [4], [], []]
        )


class StaggerTest(TestCase):
    """Tests for ``stagger()``"""

    def test_default(self):
        iterable = [0, 1, 2, 3]
        actual = list(mi.stagger(iterable))
        expected = [(None, 0, 1), (0, 1, 2), (1, 2, 3)]
        self.assertEqual(actual, expected)

    def test_offsets(self):
        iterable = [0, 1, 2, 3]
        for offsets, expected in [
            ((-2, 0, 2), [('', 0, 2), ('', 1, 3)]),
            ((-2, -1), [('', ''), ('', 0), (0, 1), (1, 2), (2, 3)]),
            ((1, 2), [(1, 2), (2, 3)]),
        ]:
            all_groups = mi.stagger(iterable, offsets=offsets, fillvalue='')
            self.assertEqual(list(all_groups), expected)

    def test_longest(self):
        iterable = [0, 1, 2, 3]
        for offsets, expected in [
            (
                (-1, 0, 1),
                [('', 0, 1), (0, 1, 2), (1, 2, 3), (2, 3, ''), (3, '', '')]
            ),
            ((-2, -1), [('', ''), ('', 0), (0, 1), (1, 2), (2, 3), (3, '')]),
            ((1, 2), [(1, 2), (2, 3), (3, '')]),
        ]:
            all_groups = mi.stagger(
                iterable, offsets=offsets, fillvalue='', longest=True
            )
            self.assertEqual(list(all_groups), expected)


class ZipOffsetTest(TestCase):
    """Tests for ``zip_offset()``"""

    def test_shortest(self):
        a_1 = [0, 1, 2, 3]
        a_2 = [0, 1, 2, 3, 4, 5]
        a_3 = [0, 1, 2, 3, 4, 5, 6, 7]
        actual = list(
            mi.zip_offset(a_1, a_2, a_3, offsets=(-1, 0, 1), fillvalue='')
        )
        expected = [('', 0, 1), (0, 1, 2), (1, 2, 3), (2, 3, 4), (3, 4, 5)]
        self.assertEqual(actual, expected)

    def test_longest(self):
        a_1 = [0, 1, 2, 3]
        a_2 = [0, 1, 2, 3, 4, 5]
        a_3 = [0, 1, 2, 3, 4, 5, 6, 7]
        actual = list(
            mi.zip_offset(a_1, a_2, a_3, offsets=(-1, 0, 1), longest=True)
        )
        expected = [
            (None, 0, 1),
            (0, 1, 2),
            (1, 2, 3),
            (2, 3, 4),
            (3, 4, 5),
            (None, 5, 6),
            (None, None, 7),
        ]
        self.assertEqual(actual, expected)

    def test_mismatch(self):
        iterables = [0, 1, 2], [2, 3, 4]
        offsets = (-1, 0, 1)
        self.assertRaises(
            ValueError,
            lambda: list(mi.zip_offset(*iterables, offsets=offsets))
        )


class SortTogetherTest(TestCase):
    """Tests for sort_together()"""

    def test_key_list(self):
        """tests `key_list` including default, iterables include duplicates"""
        iterables = [
            ['GA', 'GA', 'GA', 'CT', 'CT', 'CT'],
            ['May', 'Aug.', 'May', 'June', 'July', 'July'],
            [97, 20, 100, 70, 100, 20]
        ]

        self.assertEqual(
            mi.sort_together(iterables),
            [
                ('CT', 'CT', 'CT', 'GA', 'GA', 'GA'),
                ('June', 'July', 'July', 'May', 'Aug.', 'May'),
                (70, 100, 20, 97, 20, 100)
            ]
        )

        self.assertEqual(
            mi.sort_together(iterables, key_list=(0, 1)),
            [
                ('CT', 'CT', 'CT', 'GA', 'GA', 'GA'),
                ('July', 'July', 'June', 'Aug.', 'May', 'May'),
                (100, 20, 70, 20, 97, 100)
            ]
        )

        self.assertEqual(
            mi.sort_together(iterables, key_list=(0, 1, 2)),
            [
                ('CT', 'CT', 'CT', 'GA', 'GA', 'GA'),
                ('July', 'July', 'June', 'Aug.', 'May', 'May'),
                (20, 100, 70, 20, 97, 100)
            ]
        )

        self.assertEqual(
            mi.sort_together(iterables, key_list=(2,)),
            [
                ('GA', 'CT', 'CT', 'GA', 'GA', 'CT'),
                ('Aug.', 'July', 'June', 'May', 'May', 'July'),
                (20, 20, 70, 97, 100, 100)
            ]
        )

    def test_invalid_key_list(self):
        """tests `key_list` for indexes not available in `iterables`"""
        iterables = [
            ['GA', 'GA', 'GA', 'CT', 'CT', 'CT'],
            ['May', 'Aug.', 'May', 'June', 'July', 'July'],
            [97, 20, 100, 70, 100, 20]
        ]

        self.assertRaises(
            IndexError, lambda: mi.sort_together(iterables, key_list=(5,))
        )

    def test_reverse(self):
        """tests `reverse` to ensure a reverse sort for `key_list` iterables"""
        iterables = [
            ['GA', 'GA', 'GA', 'CT', 'CT', 'CT'],
            ['May', 'Aug.', 'May', 'June', 'July', 'July'],
            [97, 20, 100, 70, 100, 20]
        ]

        self.assertEqual(
            mi.sort_together(iterables, key_list=(0, 1, 2), reverse=True),
            [('GA', 'GA', 'GA', 'CT', 'CT', 'CT'),
             ('May', 'May', 'Aug.', 'June', 'July', 'July'),
             (100, 97, 20, 70, 100, 20)]
        )

    def test_uneven_iterables(self):
        """tests trimming of iterables to the shortest length before sorting"""
        iterables = [['GA', 'GA', 'GA', 'CT', 'CT', 'CT', 'MA'],
                     ['May', 'Aug.', 'May', 'June', 'July', 'July'],
                     [97, 20, 100, 70, 100, 20, 0]]

        self.assertEqual(
            mi.sort_together(iterables),
            [
                ('CT', 'CT', 'CT', 'GA', 'GA', 'GA'),
                ('June', 'July', 'July', 'May', 'Aug.', 'May'),
                (70, 100, 20, 97, 20, 100)
            ]
        )


class DivideTest(TestCase):
    """Tests for divide()"""

    def test_invalid_n(self):
        self.assertRaises(ValueError, lambda: mi.divide(-1, [1, 2, 3]))
        self.assertRaises(ValueError, lambda: mi.divide(0, [1, 2, 3]))

    def test_basic(self):
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

        for n, expected in [
            (1, [iterable]),
            (2, [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10]]),
            (3, [[1, 2, 3, 4], [5, 6, 7], [8, 9, 10]]),
            (10, [[n] for n in range(1, 10 + 1)]),
        ]:
            self.assertEqual(
                [list(x) for x in mi.divide(n, iterable)], expected
            )

    def test_large_n(self):
        iterable = [1, 2, 3, 4]
        self.assertEqual(
            [list(x) for x in mi.divide(6, iterable)],
            [[1], [2], [3], [4], [], []]
        )


class TestAlwaysIterable(TestCase):
    """Tests for always_iterable()"""
    def test_single(self):
        self.assertEqual(list(mi.always_iterable(1)), [1])

    def test_strings(self):
        for obj in ['foo', b'bar', u'baz']:
            actual = list(mi.always_iterable(obj))
            expected = [obj]
            self.assertEqual(actual, expected)

    def test_base_type(self):
        dict_obj = {'a': 1, 'b': 2}
        str_obj = '123'

        # Default: dicts are iterable like they normally are
        default_actual = list(mi.always_iterable(dict_obj))
        default_expected = list(dict_obj)
        self.assertEqual(default_actual, default_expected)

        # Unitary types set: dicts are not iterable
        custom_actual = list(mi.always_iterable(dict_obj, base_type=dict))
        custom_expected = [dict_obj]
        self.assertEqual(custom_actual, custom_expected)

        # With unitary types set, strings are iterable
        str_actual = list(mi.always_iterable(str_obj, base_type=None))
        str_expected = list(str_obj)
        self.assertEqual(str_actual, str_expected)

    def test_iterables(self):
        self.assertEqual(list(mi.always_iterable([0, 1])), [0, 1])
        self.assertEqual(
            list(mi.always_iterable([0, 1], base_type=list)), [[0, 1]]
        )
        self.assertEqual(
            list(mi.always_iterable(iter('foo'))), ['f', 'o', 'o']
        )
        self.assertEqual(list(mi.always_iterable([])), [])

    def test_none(self):
        self.assertEqual(list(mi.always_iterable(None)), [])

    def test_generator(self):
        def _gen():
            yield 0
            yield 1

        self.assertEqual(list(mi.always_iterable(_gen())), [0, 1])


class AdjacentTests(TestCase):
    def test_typical(self):
        actual = list(mi.adjacent(lambda x: x % 5 == 0, range(10)))
        expected = [(True, 0), (True, 1), (False, 2), (False, 3), (True, 4),
                    (True, 5), (True, 6), (False, 7), (False, 8), (False, 9)]
        self.assertEqual(actual, expected)

    def test_empty_iterable(self):
        actual = list(mi.adjacent(lambda x: x % 5 == 0, []))
        expected = []
        self.assertEqual(actual, expected)

    def test_length_one(self):
        actual = list(mi.adjacent(lambda x: x % 5 == 0, [0]))
        expected = [(True, 0)]
        self.assertEqual(actual, expected)

        actual = list(mi.adjacent(lambda x: x % 5 == 0, [1]))
        expected = [(False, 1)]
        self.assertEqual(actual, expected)

    def test_consecutive_true(self):
        """Test that when the predicate matches multiple consecutive elements
        it doesn't repeat elements in the output"""
        actual = list(mi.adjacent(lambda x: x % 5 < 2, range(10)))
        expected = [(True, 0), (True, 1), (True, 2), (False, 3), (True, 4),
                    (True, 5), (True, 6), (True, 7), (False, 8), (False, 9)]
        self.assertEqual(actual, expected)

    def test_distance(self):
        actual = list(mi.adjacent(lambda x: x % 5 == 0, range(10), distance=2))
        expected = [(True, 0), (True, 1), (True, 2), (True, 3), (True, 4),
                    (True, 5), (True, 6), (True, 7), (False, 8), (False, 9)]
        self.assertEqual(actual, expected)

        actual = list(mi.adjacent(lambda x: x % 5 == 0, range(10), distance=3))
        expected = [(True, 0), (True, 1), (True, 2), (True, 3), (True, 4),
                    (True, 5), (True, 6), (True, 7), (True, 8), (False, 9)]
        self.assertEqual(actual, expected)

    def test_large_distance(self):
        """Test distance larger than the length of the iterable"""
        iterable = range(10)
        actual = list(mi.adjacent(lambda x: x % 5 == 4, iterable, distance=20))
        expected = list(zip(repeat(True), iterable))
        self.assertEqual(actual, expected)

        actual = list(mi.adjacent(lambda x: False, iterable, distance=20))
        expected = list(zip(repeat(False), iterable))
        self.assertEqual(actual, expected)

    def test_zero_distance(self):
        """Test that adjacent() reduces to zip+map when distance is 0"""
        iterable = range(1000)
        predicate = lambda x: x % 4 == 2
        actual = mi.adjacent(predicate, iterable, 0)
        expected = zip(map(predicate, iterable), iterable)
        self.assertTrue(all(a == e for a, e in zip(actual, expected)))

    def test_negative_distance(self):
        """Test that adjacent() raises an error with negative distance"""
        pred = lambda x: x
        self.assertRaises(
            ValueError, lambda: mi.adjacent(pred, range(1000), -1)
        )
        self.assertRaises(
            ValueError, lambda: mi.adjacent(pred, range(10), -10)
        )

    def test_grouping(self):
        """Test interaction of adjacent() with groupby_transform()"""
        iterable = mi.adjacent(lambda x: x % 5 == 0, range(10))
        grouper = mi.groupby_transform(iterable, itemgetter(0), itemgetter(1))
        actual = [(k, list(g)) for k, g in grouper]
        expected = [
            (True, [0, 1]),
            (False, [2, 3]),
            (True, [4, 5, 6]),
            (False, [7, 8, 9]),
        ]
        self.assertEqual(actual, expected)

    def test_call_once(self):
        """Test that the predicate is only called once per item."""
        already_seen = set()
        iterable = range(10)

        def predicate(item):
            self.assertNotIn(item, already_seen)
            already_seen.add(item)
            return True

        actual = list(mi.adjacent(predicate, iterable))
        expected = [(True, x) for x in iterable]
        self.assertEqual(actual, expected)


class GroupByTransformTests(TestCase):
    def assertAllGroupsEqual(self, groupby1, groupby2):
        """Compare two groupby objects for equality, both keys and groups."""
        for a, b in zip(groupby1, groupby2):
            key1, group1 = a
            key2, group2 = b
            self.assertEqual(key1, key2)
            self.assertListEqual(list(group1), list(group2))
        self.assertRaises(StopIteration, lambda: next(groupby1))
        self.assertRaises(StopIteration, lambda: next(groupby2))

    def test_default_funcs(self):
        """Test that groupby_transform() with default args mimics groupby()"""
        iterable = [(x // 5, x) for x in range(1000)]
        actual = mi.groupby_transform(iterable)
        expected = groupby(iterable)
        self.assertAllGroupsEqual(actual, expected)

    def test_valuefunc(self):
        iterable = [(int(x / 5), int(x / 3), x) for x in range(10)]

        # Test the standard usage of grouping one iterable using another's keys
        grouper = mi.groupby_transform(
            iterable, keyfunc=itemgetter(0), valuefunc=itemgetter(-1)
        )
        actual = [(k, list(g)) for k, g in grouper]
        expected = [(0, [0, 1, 2, 3, 4]), (1, [5, 6, 7, 8, 9])]
        self.assertEqual(actual, expected)

        grouper = mi.groupby_transform(
            iterable, keyfunc=itemgetter(1), valuefunc=itemgetter(-1)
        )
        actual = [(k, list(g)) for k, g in grouper]
        expected = [(0, [0, 1, 2]), (1, [3, 4, 5]), (2, [6, 7, 8]), (3, [9])]
        self.assertEqual(actual, expected)

        # and now for something a little different
        d = dict(zip(range(10), 'abcdefghij'))
        grouper = mi.groupby_transform(
            range(10), keyfunc=lambda x: x // 5, valuefunc=d.get
        )
        actual = [(k, ''.join(g)) for k, g in grouper]
        expected = [(0, 'abcde'), (1, 'fghij')]
        self.assertEqual(actual, expected)

    def test_no_valuefunc(self):
        iterable = range(1000)

        def key(x):
            return x // 5

        actual = mi.groupby_transform(iterable, key, valuefunc=None)
        expected = groupby(iterable, key)
        self.assertAllGroupsEqual(actual, expected)

        actual = mi.groupby_transform(iterable, key)  # default valuefunc
        expected = groupby(iterable, key)
        self.assertAllGroupsEqual(actual, expected)


class NumericRangeTests(TestCase):
    def test_basic(self):
        for args, expected in [
            ((4,), [0, 1, 2, 3]),
            ((4.0,), [0.0, 1.0, 2.0, 3.0]),
            ((1.0, 4), [1.0, 2.0, 3.0]),
            ((1, 4.0), [1, 2, 3]),
            ((1.0, 5), [1.0, 2.0, 3.0, 4.0]),
            ((0, 20, 5), [0, 5, 10, 15]),
            ((0, 20, 5.0), [0.0, 5.0, 10.0, 15.0]),
            ((0, 10, 3), [0, 3, 6, 9]),
            ((0, 10, 3.0), [0.0, 3.0, 6.0, 9.0]),
            ((0, -5, -1), [0, -1, -2, -3, -4]),
            ((0.0, -5, -1), [0.0, -1.0, -2.0, -3.0, -4.0]),
            ((1, 2, Fraction(1, 2)), [Fraction(1, 1), Fraction(3, 2)]),
            ((0,), []),
            ((0.0,), []),
            ((1, 0), []),
            ((1.0, 0.0), []),
            ((Fraction(2, 1),), [Fraction(0, 1), Fraction(1, 1)]),
            ((Decimal('2.0'),), [Decimal('0.0'), Decimal('1.0')]),
        ]:
            actual = list(mi.numeric_range(*args))
            self.assertEqual(actual, expected)
            self.assertTrue(
                all(type(a) == type(e) for a, e in zip(actual, expected))
            )

    def test_arg_count(self):
        self.assertRaises(TypeError, lambda: list(mi.numeric_range()))
        self.assertRaises(
            TypeError, lambda: list(mi.numeric_range(0, 1, 2, 3))
        )

    def test_zero_step(self):
        self.assertRaises(
            ValueError, lambda: list(mi.numeric_range(1, 2, 0))
        )


class CountCycleTests(TestCase):
    def test_basic(self):
        expected = [
            (0, 'a'), (0, 'b'), (0, 'c'),
            (1, 'a'), (1, 'b'), (1, 'c'),
            (2, 'a'), (2, 'b'), (2, 'c'),
        ]
        for actual in [
            mi.take(9, mi.count_cycle('abc')),  # n=None
            list(mi.count_cycle('abc', 3)),  # n=3
        ]:
            self.assertEqual(actual, expected)

    def test_empty(self):
        self.assertEqual(list(mi.count_cycle('')), [])
        self.assertEqual(list(mi.count_cycle('', 2)), [])

    def test_negative(self):
        self.assertEqual(list(mi.count_cycle('abc', -3)), [])


class LocateTests(TestCase):
    def test_default_pred(self):
        iterable = [0, 1, 1, 0, 1, 0, 0]
        actual = list(mi.locate(iterable))
        expected = [1, 2, 4]
        self.assertEqual(actual, expected)

    def test_no_matches(self):
        iterable = [0, 0, 0]
        actual = list(mi.locate(iterable))
        expected = []
        self.assertEqual(actual, expected)

    def test_custom_pred(self):
        iterable = ['0', 1, 1, '0', 1, '0', '0']
        pred = lambda x: x == '0'
        actual = list(mi.locate(iterable, pred))
        expected = [0, 3, 5, 6]
        self.assertEqual(actual, expected)


class StripFunctionTests(TestCase):
    def test_hashable(self):
        iterable = list('www.example.com')
        pred = lambda x: x in set('cmowz.')

        self.assertEqual(list(mi.lstrip(iterable, pred)), list('example.com'))
        self.assertEqual(list(mi.rstrip(iterable, pred)), list('www.example'))
        self.assertEqual(list(mi.strip(iterable, pred)), list('example'))

    def test_not_hashable(self):
        iterable = [
            list('http://'), list('www'), list('.example'), list('.com')
        ]
        pred = lambda x: x in [list('http://'), list('www'), list('.com')]

        self.assertEqual(list(mi.lstrip(iterable, pred)), iterable[2:])
        self.assertEqual(list(mi.rstrip(iterable, pred)), iterable[:3])
        self.assertEqual(list(mi.strip(iterable, pred)), iterable[2: 3])

    def test_math(self):
        iterable = [0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2]
        pred = lambda x: x <= 2

        self.assertEqual(list(mi.lstrip(iterable, pred)), iterable[3:])
        self.assertEqual(list(mi.rstrip(iterable, pred)), iterable[:-3])
        self.assertEqual(list(mi.strip(iterable, pred)), iterable[3:-3])


class IsliceExtendedTests(TestCase):
    def test_all(self):
        iterable = ['0', '1', '2', '3', '4', '5']
        indexes = list(range(-4, len(iterable) + 4)) + [None]
        steps = [1, 2, 3, 4, -1, -2, -3, 4]
        for slice_args in product(indexes, indexes, steps):
            try:
                actual = list(mi.islice_extended(iterable, *slice_args))
            except Exception as e:
                self.fail((slice_args, e))

            expected = iterable[slice(*slice_args)]
            self.assertEqual(actual, expected, slice_args)

    def test_zero_step(self):
        with self.assertRaises(ValueError):
            list(mi.islice_extended([1, 2, 3], 0, 1, 0))


class ConsecutiveGroupsTest(TestCase):
    def test_numbers(self):
        iterable = [-10, -8, -7, -6, 1, 2, 4, 5, -1, 7]
        actual = [list(g) for g in mi.consecutive_groups(iterable)]
        expected = [[-10], [-8, -7, -6], [1, 2], [4, 5], [-1], [7]]
        self.assertEqual(actual, expected)

    def test_custom_ordering(self):
        iterable = ['1', '10', '11', '20', '21', '22', '30', '31']
        ordering = lambda x: int(x)
        actual = [list(g) for g in mi.consecutive_groups(iterable, ordering)]
        expected = [['1'], ['10', '11'], ['20', '21', '22'], ['30', '31']]
        self.assertEqual(actual, expected)

    def test_exotic_ordering(self):
        iterable = [
            ('a', 'b', 'c', 'd'),
            ('a', 'c', 'b', 'd'),
            ('a', 'c', 'd', 'b'),
            ('a', 'd', 'b', 'c'),
            ('d', 'b', 'c', 'a'),
            ('d', 'c', 'a', 'b'),
        ]
        ordering = list(permutations('abcd')).index
        actual = [list(g) for g in mi.consecutive_groups(iterable, ordering)]
        expected = [
            [('a', 'b', 'c', 'd')],
            [('a', 'c', 'b', 'd'), ('a', 'c', 'd', 'b'), ('a', 'd', 'b', 'c')],
            [('d', 'b', 'c', 'a'), ('d', 'c', 'a', 'b')],
        ]
        self.assertEqual(actual, expected)


class DifferenceTest(TestCase):
    def test_normal(self):
        iterable = [10, 20, 30, 40, 50]
        actual = list(mi.difference(iterable))
        expected = [10, 10, 10, 10, 10]
        self.assertEqual(actual, expected)

    def test_custom(self):
        iterable = [10, 20, 30, 40, 50]
        actual = list(mi.difference(iterable, add))
        expected = [10, 30, 50, 70, 90]
        self.assertEqual(actual, expected)

    def test_roundtrip(self):
        original = list(range(100))
        accumulated = mi.accumulate(original)
        actual = list(mi.difference(accumulated))
        self.assertEqual(actual, original)

    def test_one(self):
        self.assertEqual(list(mi.difference([0])), [0])

    def test_empty(self):
        self.assertEqual(list(mi.difference([])), [])


class SeekableTest(TestCase):
    def test_exhaustion_reset(self):
        iterable = [str(n) for n in range(10)]

        s = mi.seekable(iterable)
        self.assertEqual(list(s), iterable)  # Normal iteration
        self.assertEqual(list(s), [])  # Iterable is exhausted

        s.seek(0)
        self.assertEqual(list(s), iterable)  # Back in action

    def test_partial_reset(self):
        iterable = [str(n) for n in range(10)]

        s = mi.seekable(iterable)
        self.assertEqual(mi.take(5, s), iterable[:5])  # Normal iteration

        s.seek(1)
        self.assertEqual(list(s), iterable[1:])  # Get the rest of the iterable

    def test_forward(self):
        iterable = [str(n) for n in range(10)]

        s = mi.seekable(iterable)
        self.assertEqual(mi.take(1, s), iterable[:1])  # Normal iteration

        s.seek(3)  # Skip over index 2
        self.assertEqual(list(s), iterable[3:])  # Result is similar to slicing

        s.seek(0)  # Back to 0
        self.assertEqual(list(s), iterable)  # No difference in result

    def test_past_end(self):
        iterable = [str(n) for n in range(10)]

        s = mi.seekable(iterable)
        self.assertEqual(mi.take(1, s), iterable[:1])  # Normal iteration

        s.seek(20)
        self.assertEqual(list(s), [])  # Iterable is exhausted

        s.seek(0)  # Back to 0
        self.assertEqual(list(s), iterable)  # No difference in result


class RunLengthTest(TestCase):
    def test_encode(self):
        iterable = (int(str(n)[0]) for n in count(800))
        actual = mi.take(4, mi.run_length.encode(iterable))
        expected = [(8, 100), (9, 100), (1, 1000), (2, 1000)]
        self.assertEqual(actual, expected)

    def test_decode(self):
        iterable = [('d', 4), ('c', 3), ('b', 2), ('a', 1)]
        actual = ''.join(mi.run_length.decode(iterable))
        expected = 'ddddcccbba'
        self.assertEqual(actual, expected)


class ExactlyNTests(TestCase):
    """Tests for ``exactly_n()``"""

    def test_true(self):
        """Iterable has ``n`` ``True`` elements"""
        self.assertTrue(mi.exactly_n([True, False, True], 2))
        self.assertTrue(mi.exactly_n([1, 1, 1, 0], 3))
        self.assertTrue(mi.exactly_n([False, False], 0))
        self.assertTrue(mi.exactly_n(range(100), 10, lambda x: x < 10))

    def test_false(self):
        """Iterable does not have ``n`` ``True`` elements"""
        self.assertFalse(mi.exactly_n([True, False, False], 2))
        self.assertFalse(mi.exactly_n([True, True, False], 1))
        self.assertFalse(mi.exactly_n([False], 1))
        self.assertFalse(mi.exactly_n([True], -1))
        self.assertFalse(mi.exactly_n(repeat(True), 100))

    def test_empty(self):
        """Return ``True`` if the iterable is empty and ``n`` is 0"""
        self.assertTrue(mi.exactly_n([], 0))
        self.assertFalse(mi.exactly_n([], 1))