test_more.py

from collections import OrderedDict
from decimal import Decimal
from doctest import DocTestSuite
from fractions import Fraction
from functools import partial, reduce
from heapq import merge
from io import StringIO
from itertools import (
    accumulate,
    chain,
    count,
    groupby,
    islice,
    permutations,
    product,
    repeat,
)
from operator import add, mul, itemgetter
from time import sleep
from unittest import TestCase

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)

    def test_alias(self):
        self.assertNotEqual(merge.__doc__, mi.collate.__doc__)
        self.assertNotEqual(partial.__doc__, mi.collate.__doc__)


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 IterOnlyRange:
    """User-defined iterable class which only support __iter__.

    >>> r = IterOnlyRange(5)
    >>> r[0]
    AttributeError: IterOnlyRange instance has no attribute '__getitem__'

    Note: In Python 3, ``TypeError`` will be raised because ``object`` is
    inherited implicitly by default.

    >>> r[0]
    TypeError: 'IterOnlyRange' object does not support indexing
    """
    def __init__(self, n):
        """Set the length of the range."""
        self.n = n

    def __iter__(self):
        """Works same as range()."""
        return iter(range(self.n))


class LastTests(TestCase):
    """Tests for ``last()``"""

    def test_many_nonsliceable(self):
        """Test that it works on many-item non-slice-able iterables."""
        # Also try it on a generator expression to make sure it works on
        # whatever those return, across Python versions.
        self.assertEqual(mi.last(x for x in range(4)), 3)

    def test_one_nonsliceable(self):
        """Test that it doesn't raise StopIteration prematurely."""
        self.assertEqual(mi.last(x for x in range(1)), 0)

    def test_empty_stop_iteration_nonsliceable(self):
        """It should raise ValueError for empty non-slice-able iterables."""
        self.assertRaises(ValueError, lambda: mi.last(x for x in range(0)))

    def test_default_nonsliceable(self):
        """It should return the provided default arg for empty non-slice-able
        iterables.
        """
        self.assertEqual(mi.last((x for x in range(0)), 'boo'), 'boo')

    def test_many_sliceable(self):
        """Test that it works on many-item slice-able iterables."""
        self.assertEqual(mi.last([0, 1, 2, 3]), 3)

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

    def test_empty_stop_iteration_sliceable(self):
        """It should raise ValueError for empty slice-able iterables."""
        self.assertRaises(ValueError, lambda: mi.last([]))

    def test_default_sliceable(self):
        """It should return the provided default arg for empty slice-able
        iterables.
        """
        self.assertEqual(mi.last([], 'boo'), 'boo')

    def test_dict(self):
        """last(dic) and last(dic.keys()) should return same result."""
        dic = {'a': 1, 'b': 2, 'c': 3}
        self.assertEqual(mi.last(dic), mi.last(dic.keys()))

    def test_ordereddict(self):
        """last(dic) should return the last key."""
        od = OrderedDict()
        od['a'] = 1
        od['b'] = 2
        od['c'] = 3
        self.assertEqual(mi.last(od), 'c')

    def test_customrange(self):
        """It should work on custom class where [] raises AttributeError."""
        self.assertEqual(mi.last(IterOnlyRange(5)), 4)


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)

    def test_other_iterables(self):
        """Make sure ``distinct_permutations()`` accepts a different type of
        iterables.

        """
        # a generator
        iterable = (c for c in ['z', 'a', 'a', 'q', 'q', 'q', 'y'])
        test_output = sorted(mi.distinct_permutations(iterable))
        # "reload" it
        iterable = (c for c in ['z', 'a', 'a', 'q', 'q', 'q', 'y'])
        ref_output = sorted(set(permutations(iterable)))
        self.assertEqual(test_output, ref_output)

        # an iterator
        iterable = iter(['z', 'a', 'a', 'q', 'q', 'q', 'y'])
        test_output = sorted(mi.distinct_permutations(iterable))
        # "reload" it
        iterable = iter(['z', 'a', 'a', 'q', 'q', 'q', 'y'])
        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.assertTrue(s.closed)


class OneTests(TestCase):
    def test_basic(self):
        it = iter(['item'])
        self.assertEqual(mi.one(it), 'item')

    def test_too_short(self):
        it = iter([])
        self.assertRaises(ValueError, lambda: mi.one(it))
        self.assertRaises(IndexError, lambda: mi.one(it, too_short=IndexError))

    def test_too_long(self):
        it = count()
        self.assertRaises(ValueError, lambda: mi.one(it))  # burn 0 and 1
        self.assertEqual(next(it), 2)
        self.assertRaises(
            OverflowError, lambda: mi.one(it, too_long=OverflowError)
        )


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 SubstringsTests(TestCase):
    def test_basic(self):
        iterable = (x for x in range(4))
        actual = list(mi.substrings(iterable))
        expected = [
            (0,),
            (1,),
            (2,),
            (3,),
            (0, 1),
            (1, 2),
            (2, 3),
            (0, 1, 2),
            (1, 2, 3),
            (0, 1, 2, 3),
        ]
        self.assertEqual(actual, expected)

    def test_strings(self):
        iterable = 'abc'
        actual = list(mi.substrings(iterable))
        expected = [
            ('a',), ('b',), ('c',), ('a', 'b'), ('b', 'c'), ('a', 'b', 'c')
        ]
        self.assertEqual(actual, expected)

    def test_empty(self):
        iterable = iter([])
        actual = list(mi.substrings(iterable))
        expected = []
        self.assertEqual(actual, expected)

    def test_order(self):
        iterable = [2, 0, 1]
        actual = list(mi.substrings(iterable))
        expected = [(2,), (0,), (1,), (2, 0), (0, 1), (2, 0, 1)]
        self.assertEqual(actual, expected)


class SubstringsIndexesTests(TestCase):
    def test_basic(self):
        sequence = [x for x in range(4)]
        actual = list(mi.substrings_indexes(sequence))
        expected = [
            ([0], 0, 1),
            ([1], 1, 2),
            ([2], 2, 3),
            ([3], 3, 4),
            ([0, 1], 0, 2),
            ([1, 2], 1, 3),
            ([2, 3], 2, 4),
            ([0, 1, 2], 0, 3),
            ([1, 2, 3], 1, 4),
            ([0, 1, 2, 3], 0, 4),
        ]
        self.assertEqual(actual, expected)

    def test_strings(self):
        sequence = 'abc'
        actual = list(mi.substrings_indexes(sequence))
        expected = [
            ('a', 0, 1),
            ('b', 1, 2),
            ('c', 2, 3),
            ('ab', 0, 2),
            ('bc', 1, 3),
            ('abc', 0, 3),
        ]
        self.assertEqual(actual, expected)

    def test_empty(self):
        sequence = []
        actual = list(mi.substrings_indexes(sequence))
        expected = []
        self.assertEqual(actual, expected)

    def test_order(self):
        sequence = [2, 0, 1]
        actual = list(mi.substrings_indexes(sequence))
        expected = [
            ([2], 0, 1),
            ([0], 1, 2),
            ([1], 2, 3),
            ([2, 0], 0, 2),
            ([0, 1], 1, 3),
            ([2, 0, 1], 0, 3),
        ]
        self.assertEqual(actual, expected)

    def test_reverse(self):
        sequence = [2, 0, 1]
        actual = list(mi.substrings_indexes(sequence, reverse=True))
        expected = [
            ([2, 0, 1], 0, 3),
            ([2, 0], 0, 2),
            ([0, 1], 1, 3),
            ([2], 0, 1),
            ([0], 1, 2),
            ([1], 2, 3),
        ]
        self.assertEqual(actual, expected)


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.assertIn(10, D)
        self.assertNotIn(40, D)
        self.assertIn(20, D)
        self.assertNotIn(21, 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 InterleaveTests(TestCase):
    def test_even(self):
        actual = list(mi.interleave([1, 4, 7], [2, 5, 8], [3, 6, 9]))
        expected = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        self.assertEqual(actual, expected)

    def test_short(self):
        actual = list(mi.interleave([1, 4], [2, 5, 7], [3, 6, 8]))
        expected = [1, 2, 3, 4, 5, 6]
        self.assertEqual(actual, expected)

    def test_mixed_types(self):
        it_list = ['a', 'b', 'c', 'd']
        it_str = '12345'
        it_inf = count()
        actual = list(mi.interleave(it_list, it_str, it_inf))
        expected = ['a', '1', 0, 'b', '2', 1, 'c', '3', 2, 'd', '4', 3]
        self.assertEqual(actual, expected)


class InterleaveLongestTests(TestCase):
    def test_even(self):
        actual = list(mi.interleave_longest([1, 4, 7], [2, 5, 8], [3, 6, 9]))
        expected = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        self.assertEqual(actual, expected)

    def test_short(self):
        actual = list(mi.interleave_longest([1, 4], [2, 5, 7], [3, 6, 8]))
        expected = [1, 2, 3, 4, 5, 6, 7, 8]
        self.assertEqual(actual, expected)

    def test_mixed_types(self):
        it_list = ['a', 'b', 'c', 'd']
        it_str = '12345'
        it_gen = (x for x in range(3))
        actual = list(mi.interleave_longest(it_list, it_str, it_gen))
        expected = ['a', '1', 0, 'b', '2', 1, 'c', '3', 2, 'd', '4', '5']
        self.assertEqual(actual, expected)


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_to_bytes(self):
        l = [[b"s1"], b"s2", [[b"s3"], b"s4"], [[[b"s5"]]]]
        self.assertEqual(
            list(mi.collapse(l)), [b"s1", b"s2", b"s3", b"s4", b"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 'a'
            yield '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, ['HEADER\na\n', '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, '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 SplitAtTests(TestCase):
    """Tests for ``split()``"""

    def comp_with_str_split(self, str_to_split, delim):
        pred = lambda c: c == delim
        actual = list(map(''.join, mi.split_at(str_to_split, pred)))
        expected = str_to_split.split(delim)
        self.assertEqual(actual, expected)

    def test_seperators(self):
        test_strs = ['', 'abcba', 'aaabbbcccddd', 'e']
        for s, delim in product(test_strs, 'abcd'):
            self.comp_with_str_split(s, delim)


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 SplitIntoTests(TestCase):
    """Tests for ``split_into()``"""

    def test_iterable_just_right(self):
        """Size of ``iterable`` equals the sum of ``sizes``."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [2, 3, 4]
        expected = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_iterable_too_small(self):
        """Size of ``iterable`` is smaller than sum of ``sizes``. Last return
        list is shorter as a result."""
        iterable = [1, 2, 3, 4, 5, 6, 7]
        sizes = [2, 3, 4]
        expected = [[1, 2], [3, 4, 5], [6, 7]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_iterable_too_small_extra(self):
        """Size of ``iterable`` is smaller than sum of ``sizes``. Second last
        return list is shorter and last return list is empty as a result."""
        iterable = [1, 2, 3, 4, 5, 6, 7]
        sizes = [2, 3, 4, 5]
        expected = [[1, 2], [3, 4, 5], [6, 7], []]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_iterable_too_large(self):
        """Size of ``iterable`` is larger than sum of ``sizes``. Not all
        items of iterable are returned."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [2, 3, 2]
        expected = [[1, 2], [3, 4, 5], [6, 7]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_using_none_with_leftover(self):
        """Last item of ``sizes`` is None when items still remain in
        ``iterable``. Last list returned stretches to fit all remaining items
        of ``iterable``."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [2, 3, None]
        expected = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_using_none_without_leftover(self):
        """Last item of ``sizes`` is None when no items remain in
        ``iterable``. Last list returned is empty."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [2, 3, 4, None]
        expected = [[1, 2], [3, 4, 5], [6, 7, 8, 9], []]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_using_none_mid_sizes(self):
        """None is present in ``sizes`` but is not the last item. Last list
        returned stretches to fit all remaining items of ``iterable`` but
        all items in ``sizes`` after None are ignored."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [2, 3, None, 4]
        expected = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_iterable_empty(self):
        """``iterable`` argument is empty but ``sizes`` is not. An empty
        list is returned for each item in ``sizes``."""
        iterable = []
        sizes = [2, 4, 2]
        expected = [[], [], []]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_iterable_empty_using_none(self):
        """``iterable`` argument is empty but ``sizes`` is not. An empty
        list is returned for each item in ``sizes`` that is not after a
        None item."""
        iterable = []
        sizes = [2, 4, None, 2]
        expected = [[], [], []]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_sizes_empty(self):
        """``sizes`` argument is empty but ``iterable`` is not. An empty
        generator is returned."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = []
        expected = []
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_both_empty(self):
        """Both ``sizes`` and ``iterable`` arguments are empty. An empty
        generator is returned."""
        iterable = []
        sizes = []
        expected = []
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_bool_in_sizes(self):
        """A bool object is present in ``sizes`` is treated as a 1 or 0 for
        ``True`` or ``False`` due to bool being an instance of int."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [3, True, 2, False]
        expected = [[1, 2, 3], [4], [5, 6], []]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_invalid_in_sizes(self):
        """A ValueError is raised if an object in ``sizes`` is neither ``None``
        or an integer."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [1, [], 3]
        with self.assertRaises(ValueError):
            list(mi.split_into(iterable, sizes))

    def test_invalid_in_sizes_after_none(self):
        """A item in ``sizes`` that is invalid will not raise a TypeError if it
        comes after a ``None`` item."""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = [3, 4, None, []]
        expected = [[1, 2, 3], [4, 5, 6, 7], [8, 9]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

    def test_generator_iterable_integrity(self):
        """Check that if ``iterable`` is an iterator, it is consumed only by as
        many items as the sum of ``sizes``."""
        iterable = (i for i in range(10))
        sizes = [2, 3]

        expected = [[0, 1], [2, 3, 4]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

        iterable_expected = [5, 6, 7, 8, 9]
        iterable_actual = list(iterable)
        self.assertEqual(iterable_actual, iterable_expected)

    def test_generator_sizes_integrity(self):
        """Check that if ``sizes`` is an iterator, it is consumed only until a
        ``None`` item is reached"""
        iterable = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        sizes = (i for i in [1, 2, None, 3, 4])

        expected = [[1], [2, 3], [4, 5, 6, 7, 8, 9]]
        actual = list(mi.split_into(iterable, sizes))
        self.assertEqual(actual, expected)

        sizes_expected = [3, 4]
        sizes_actual = list(sizes)
        self.assertEqual(sizes_actual, sizes_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 UnzipTests(TestCase):
    """Tests for unzip()"""

    def test_empty_iterable(self):
        self.assertEqual(list(mi.unzip([])), [])
        # in reality zip([], [], []) is equivalent to iter([])
        # but it doesn't hurt to test both
        self.assertEqual(list(mi.unzip(zip([], [], []))), [])

    def test_length_one_iterable(self):
        xs, ys, zs = mi.unzip(zip([1], [2], [3]))
        self.assertEqual(list(xs), [1])
        self.assertEqual(list(ys), [2])
        self.assertEqual(list(zs), [3])

    def test_normal_case(self):
        xs, ys, zs = range(10), range(1, 11), range(2, 12)
        zipped = zip(xs, ys, zs)
        xs, ys, zs = mi.unzip(zipped)
        self.assertEqual(list(xs), list(range(10)))
        self.assertEqual(list(ys), list(range(1, 11)))
        self.assertEqual(list(zs), list(range(2, 12)))

    def test_improperly_zipped(self):
        zipped = iter([(1, 2, 3), (4, 5), (6,)])
        xs, ys, zs = mi.unzip(zipped)
        self.assertEqual(list(xs), [1, 4, 6])
        self.assertEqual(list(ys), [2, 5])
        self.assertEqual(list(zs), [3])

    def test_increasingly_zipped(self):
        zipped = iter([(1, 2), (3, 4, 5), (6, 7, 8, 9)])
        unzipped = mi.unzip(zipped)
        # from the docstring:
        # len(first tuple) is the number of iterables zipped
        self.assertEqual(len(unzipped), 2)
        xs, ys = unzipped
        self.assertEqual(list(xs), [1, 3, 6])
        self.assertEqual(list(ys), [2, 4, 7])


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', '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)

    def test_window_size(self):
        iterable = ['0', 1, 1, '0', 1, '0', '0']
        pred = lambda *args: args == ('0', 1)
        actual = list(mi.locate(iterable, pred, window_size=2))
        expected = [0, 3]
        self.assertEqual(actual, expected)

    def test_window_size_large(self):
        iterable = [1, 2, 3, 4]
        pred = lambda a, b, c, d, e: True
        actual = list(mi.locate(iterable, pred, window_size=5))
        expected = [0]
        self.assertEqual(actual, expected)

    def test_window_size_zero(self):
        iterable = [1, 2, 3, 4]
        pred = lambda: True
        with self.assertRaises(ValueError):
            list(mi.locate(iterable, pred, window_size=0))


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 = 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

    def test_elements(self):
        iterable = map(str, count())

        s = mi.seekable(iterable)
        mi.take(10, s)

        elements = s.elements()
        self.assertEqual(
            [elements[i] for i in range(10)], [str(n) for n in range(10)]
        )
        self.assertEqual(len(elements), 10)

        mi.take(10, s)
        self.assertEqual(list(elements), [str(n) for n in range(20)])


class SequenceViewTests(TestCase):
    def test_init(self):
        view = mi.SequenceView((1, 2, 3))
        self.assertEqual(repr(view), "SequenceView((1, 2, 3))")
        self.assertRaises(TypeError, lambda: mi.SequenceView({}))

    def test_update(self):
        seq = [1, 2, 3]
        view = mi.SequenceView(seq)
        self.assertEqual(len(view), 3)
        self.assertEqual(repr(view), "SequenceView([1, 2, 3])")

        seq.pop()
        self.assertEqual(len(view), 2)
        self.assertEqual(repr(view), "SequenceView([1, 2])")

    def test_indexing(self):
        seq = ('a', 'b', 'c', 'd', 'e', 'f')
        view = mi.SequenceView(seq)
        for i in range(-len(seq), len(seq)):
            self.assertEqual(view[i], seq[i])

    def test_slicing(self):
        seq = ('a', 'b', 'c', 'd', 'e', 'f')
        view = mi.SequenceView(seq)
        n = len(seq)
        indexes = list(range(-n - 1, n + 1)) + [None]
        steps = list(range(-n, n + 1))
        steps.remove(0)
        for slice_args in product(indexes, indexes, steps):
            i = slice(*slice_args)
            self.assertEqual(view[i], seq[i])

    def test_abc_methods(self):
        # collections.Sequence should provide all of this functionality
        seq = ('a', 'b', 'c', 'd', 'e', 'f', 'f')
        view = mi.SequenceView(seq)

        # __contains__
        self.assertIn('b', view)
        self.assertNotIn('g', view)

        # __iter__
        self.assertEqual(list(iter(view)), list(seq))

        # __reversed__
        self.assertEqual(list(reversed(view)), list(reversed(seq)))

        # index
        self.assertEqual(view.index('b'), 1)

        # count
        self.assertEqual(seq.count('f'), 2)


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))


class AlwaysReversibleTests(TestCase):
    """Tests for ``always_reversible()``"""

    def test_regular_reversed(self):
        self.assertEqual(list(reversed(range(10))),
                         list(mi.always_reversible(range(10))))
        self.assertEqual(list(reversed([1, 2, 3])),
                         list(mi.always_reversible([1, 2, 3])))
        self.assertEqual(reversed([1, 2, 3]).__class__,
                         mi.always_reversible([1, 2, 3]).__class__)

    def test_nonseq_reversed(self):
        # Create a non-reversible generator from a sequence
        with self.assertRaises(TypeError):
            reversed(x for x in range(10))

        self.assertEqual(list(reversed(range(10))),
                         list(mi.always_reversible(x for x in range(10))))
        self.assertEqual(list(reversed([1, 2, 3])),
                         list(mi.always_reversible(x for x in [1, 2, 3])))
        self.assertNotEqual(reversed((1, 2)).__class__,
                            mi.always_reversible(x for x in (1, 2)).__class__)


class CircularShiftsTests(TestCase):
    def test_empty(self):
        # empty iterable -> empty list
        self.assertEqual(list(mi.circular_shifts([])), [])

    def test_simple_circular_shifts(self):
        # test the a simple iterator case
        self.assertEqual(
            mi.circular_shifts(range(4)),
            [(0, 1, 2, 3), (1, 2, 3, 0), (2, 3, 0, 1), (3, 0, 1, 2)]
        )

    def test_duplicates(self):
        # test non-distinct entries
        self.assertEqual(
            mi.circular_shifts([0, 1, 0, 1]),
            [(0, 1, 0, 1), (1, 0, 1, 0), (0, 1, 0, 1), (1, 0, 1, 0)]
        )


class MakeDecoratorTests(TestCase):
    def test_basic(self):
        slicer = mi.make_decorator(islice)

        @slicer(1, 10, 2)
        def user_function(arg_1, arg_2, kwarg_1=None):
            self.assertEqual(arg_1, 'arg_1')
            self.assertEqual(arg_2, 'arg_2')
            self.assertEqual(kwarg_1, 'kwarg_1')
            return map(str, count())

        it = user_function('arg_1', 'arg_2', kwarg_1='kwarg_1')
        actual = list(it)
        expected = ['1', '3', '5', '7', '9']
        self.assertEqual(actual, expected)

    def test_result_index(self):
        def stringify(*args, **kwargs):
            self.assertEqual(args[0], 'arg_0')
            iterable = args[1]
            self.assertEqual(args[2], 'arg_2')
            self.assertEqual(kwargs['kwarg_1'], 'kwarg_1')
            return map(str, iterable)

        stringifier = mi.make_decorator(stringify, result_index=1)

        @stringifier('arg_0', 'arg_2', kwarg_1='kwarg_1')
        def user_function(n):
            return count(n)

        it = user_function(1)
        actual = mi.take(5, it)
        expected = ['1', '2', '3', '4', '5']
        self.assertEqual(actual, expected)

    def test_wrap_class(self):
        seeker = mi.make_decorator(mi.seekable)

        @seeker()
        def user_function(n):
            return map(str, range(n))

        it = user_function(5)
        self.assertEqual(list(it), ['0', '1', '2', '3', '4'])

        it.seek(0)
        self.assertEqual(list(it), ['0', '1', '2', '3', '4'])


class MapReduceTests(TestCase):
    def test_default(self):
        iterable = (str(x) for x in range(5))
        keyfunc = lambda x: int(x) // 2
        actual = sorted(mi.map_reduce(iterable, keyfunc).items())
        expected = [(0, ['0', '1']), (1, ['2', '3']), (2, ['4'])]
        self.assertEqual(actual, expected)

    def test_valuefunc(self):
        iterable = (str(x) for x in range(5))
        keyfunc = lambda x: int(x) // 2
        valuefunc = int
        actual = sorted(mi.map_reduce(iterable, keyfunc, valuefunc).items())
        expected = [(0, [0, 1]), (1, [2, 3]), (2, [4])]
        self.assertEqual(actual, expected)

    def test_reducefunc(self):
        iterable = (str(x) for x in range(5))
        keyfunc = lambda x: int(x) // 2
        valuefunc = int
        reducefunc = lambda value_list: reduce(mul, value_list, 1)
        actual = sorted(
            mi.map_reduce(iterable, keyfunc, valuefunc, reducefunc).items()
        )
        expected = [(0, 0), (1, 6), (2, 4)]
        self.assertEqual(actual, expected)

    def test_ret(self):
        d = mi.map_reduce([1, 0, 2, 0, 1, 0], bool)
        self.assertEqual(d, {False: [0, 0, 0], True: [1, 2, 1]})
        self.assertRaises(KeyError, lambda: d[None].append(1))


class RlocateTests(TestCase):
    def test_default_pred(self):
        iterable = [0, 1, 1, 0, 1, 0, 0]
        for it in (iterable[:], iter(iterable)):
            actual = list(mi.rlocate(it))
            expected = [4, 2, 1]
            self.assertEqual(actual, expected)

    def test_no_matches(self):
        iterable = [0, 0, 0]
        for it in (iterable[:], iter(iterable)):
            actual = list(mi.rlocate(it))
            expected = []
            self.assertEqual(actual, expected)

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

    def test_efficient_reversal(self):
        iterable = range(9 ** 9)  # Is efficiently reversible
        target = 9 ** 9 - 2
        pred = lambda x: x == target  # Find-able from the right
        actual = next(mi.rlocate(iterable, pred))
        self.assertEqual(actual, target)

    def test_window_size(self):
        iterable = ['0', 1, 1, '0', 1, '0', '0']
        pred = lambda *args: args == ('0', 1)
        for it in (iterable, iter(iterable)):
            actual = list(mi.rlocate(it, pred, window_size=2))
            expected = [3, 0]
            self.assertEqual(actual, expected)

    def test_window_size_large(self):
        iterable = [1, 2, 3, 4]
        pred = lambda a, b, c, d, e: True
        for it in (iterable, iter(iterable)):
            actual = list(mi.rlocate(iterable, pred, window_size=5))
            expected = [0]
            self.assertEqual(actual, expected)

    def test_window_size_zero(self):
        iterable = [1, 2, 3, 4]
        pred = lambda: True
        for it in (iterable, iter(iterable)):
            with self.assertRaises(ValueError):
                list(mi.locate(iterable, pred, window_size=0))


class ReplaceTests(TestCase):
    def test_basic(self):
        iterable = range(10)
        pred = lambda x: x % 2 == 0
        substitutes = []
        actual = list(mi.replace(iterable, pred, substitutes))
        expected = [1, 3, 5, 7, 9]
        self.assertEqual(actual, expected)

    def test_count(self):
        iterable = range(10)
        pred = lambda x: x % 2 == 0
        substitutes = []
        actual = list(mi.replace(iterable, pred, substitutes, count=4))
        expected = [1, 3, 5, 7, 8, 9]
        self.assertEqual(actual, expected)

    def test_window_size(self):
        iterable = range(10)
        pred = lambda *args: args == (0, 1, 2)
        substitutes = []
        actual = list(mi.replace(iterable, pred, substitutes, window_size=3))
        expected = [3, 4, 5, 6, 7, 8, 9]
        self.assertEqual(actual, expected)

    def test_window_size_end(self):
        iterable = range(10)
        pred = lambda *args: args == (7, 8, 9)
        substitutes = []
        actual = list(mi.replace(iterable, pred, substitutes, window_size=3))
        expected = [0, 1, 2, 3, 4, 5, 6]
        self.assertEqual(actual, expected)

    def test_window_size_count(self):
        iterable = range(10)
        pred = lambda *args: (args == (0, 1, 2)) or (args == (7, 8, 9))
        substitutes = []
        actual = list(
            mi.replace(iterable, pred, substitutes, count=1, window_size=3)
        )
        expected = [3, 4, 5, 6, 7, 8, 9]
        self.assertEqual(actual, expected)

    def test_window_size_large(self):
        iterable = range(4)
        pred = lambda a, b, c, d, e: True
        substitutes = [5, 6, 7]
        actual = list(mi.replace(iterable, pred, substitutes, window_size=5))
        expected = [5, 6, 7]
        self.assertEqual(actual, expected)

    def test_window_size_zero(self):
        iterable = range(10)
        pred = lambda *args: True
        substitutes = []
        with self.assertRaises(ValueError):
            list(mi.replace(iterable, pred, substitutes, window_size=0))

    def test_iterable_substitutes(self):
        iterable = range(5)
        pred = lambda x: x % 2 == 0
        substitutes = iter('__')
        actual = list(mi.replace(iterable, pred, substitutes))
        expected = ['_', '_', 1, '_', '_', 3, '_', '_']
        self.assertEqual(actual, expected)


class PartitionsTest(TestCase):
    def test_types(self):
        for iterable in [
            'abcd',
            ['a', 'b', 'c', 'd'],
            ('a', 'b', 'c', 'd'),
        ]:
            with self.subTest(iterable=iterable):
                actual = list(mi.partitions(iterable))
                expected = [
                    [['a', 'b', 'c', 'd']],
                    [['a'], ['b', 'c', 'd']],
                    [['a', 'b'], ['c', 'd']],
                    [['a', 'b', 'c'], ['d']],
                    [['a'], ['b'], ['c', 'd']],
                    [['a'], ['b', 'c'], ['d']],
                    [['a', 'b'], ['c'], ['d']],
                    [['a'], ['b'], ['c'], ['d']]
                ]
                self.assertEqual(actual, expected)

    def test_empty(self):
        iterable = []
        actual = list(mi.partitions(iterable))
        expected = [[[]]]
        self.assertEqual(actual, expected)

    def test_order(self):
        iterable = iter([3, 2, 1])
        actual = list(mi.partitions(iterable))
        expected = [
            [[3, 2, 1]],
            [[3], [2, 1]],
            [[3, 2], [1]],
            [[3], [2], [1]],
        ]
        self.assertEqual(actual, expected)

    def test_duplicates(self):
        iterable = [1, 1, 1]
        actual = list(mi.partitions(iterable))
        expected = [
            [[1, 1, 1]],
            [[1], [1, 1]],
            [[1, 1], [1]],
            [[1], [1], [1]],
        ]
        self.assertEqual(actual, expected)


class TimeLimitedTests(TestCase):
    def test_basic(self):
        def generator():
            yield 1
            yield 2
            sleep(0.2)
            yield 3

        iterable = generator()
        actual = list(mi.time_limited(0.1, iterable))
        expected = [1, 2]
        self.assertEqual(actual, expected)

    def test_zero_limit(self):
        iterable = count()
        actual = list(mi.time_limited(0, iterable))
        expected = []
        self.assertEqual(actual, expected)

    def test_invalid_limit(self):
        with self.assertRaises(ValueError):
            list(mi.time_limited(-0.1, count()))


class OnlyTests(TestCase):
    def test_defaults(self):
        self.assertEqual(mi.only([]), None)
        self.assertEqual(mi.only([1]), 1)
        self.assertRaises(ValueError, lambda: mi.only([1, 2]))

    def test_custom_value(self):
        self.assertEqual(mi.only([], default='!'), '!')
        self.assertEqual(mi.only([1], default='!'), 1)
        self.assertRaises(ValueError, lambda: mi.only([1, 2], default='!'))

    def test_custom_exception(self):
        self.assertEqual(mi.only([], too_long=RuntimeError), None)
        self.assertEqual(mi.only([1], too_long=RuntimeError), 1)
        self.assertRaises(
            RuntimeError, lambda: mi.only([1, 2], too_long=RuntimeError)
        )