diff --git a/src/couch_tests_combinatorics.erl b/src/couch_tests_combinatorics.erl
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+% Licensed under the Apache License, Version 2.0 (the "License"); you may not
+% use this file except in compliance with the License. You may obtain a copy of
+% the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+% License for the specific language governing permissions and limitations under
+% the License.
+
+-module(couch_tests_combinatorics).
+
+-export([
+    powerset/1,
+    permutations/1,
+    product/1,
+    binary_combinations/1,
+    n_combinations/2
+]).
+
+%% @doc powerset(Items)
+%% Generate powerset for a given list of Items
+%% By Hynek - Pichi - Vychodil
+%% For example:
+%%   1> powerset([foo, bar, baz]).
+%%      [
+%%          [foo],
+%%          [foo,baz],
+%%          [foo,bar,baz],
+%%          [foo,bar],
+%%          [bar],
+%%          [bar,baz],
+%%          [baz],
+%%          []
+%%      ]
+-spec powerset(Elements :: list()) -> [list()].
+
+powerset([]) ->
+    [[]];
+powerset([H | T]) ->
+    PT = powerset(T),
+    powerset(H, PT, PT).
+
+powerset(_, [], Acc) ->
+    Acc;
+powerset(X, [H | T], Acc) ->
+    powerset(X, T, [[X | H] | Acc]).
+
+%% @doc permutations(Items)
+%% Return all premutations of given list of Items.
+%% from http://erlang.org/doc/programming_examples/list_comprehensions.html
+%% For example:
+%%   1> permutations([foo, bar, baz]).
+%%      [
+%%          [foo, bar, baz],
+%%          [foo, baz, bar],
+%%          [bar, foo, baz],
+%%          [bar, baz, foo],
+%%          [baz, foo, bar],
+%%          [baz, bar, foo]
+%%      ]
+-spec permutations(Elements :: list()) -> [list()].
+
+permutations([]) ->
+    [[]];
+permutations(L)  ->
+    [[H | T] || H <- L, T <- permutations(L -- [H])].
+
+%% @doc product({Items1, Items2, ..., ItemsN})
+%% Return cartesian product of multiple sets represented as list of lists
+%% From: http://stackoverflow.com/a/23886680
+%% For example:
+%%   1> product([[foo, bar], [1,2,3]]).
+%%      [
+%%        [foo, 1],
+%%        [foo, 2],
+%%        [foo, 3],
+%%        [bar, 1],
+%%        [bar, 2],
+%%        [bar, 3]
+%%      ]
+-spec product(Elements :: list()) -> [list()].
+
+product([H])   ->
+    [[A] || A <- H];
+product([H | T]) ->
+    [[A | B] || A <- H, B <- product(T)].
+
+%% @doc binary_combinations(NBits).
+%% Generate all combinations of true and false for specified number of bits.
+%% For example:
+%%   1> binary_combinations(3).
+%%      [
+%%       [ false , false , false ],
+%%       [ false , false , true  ],
+%%       [ false , true  , false ],
+%%       [ false , true  , true  ],
+%%       [ true  , false , false ],
+%%       [ true  , false , true  ],
+%%       [ true  , true  , false ],
+%%       [ true  , true  , true  ]
+%%      ]
+%%   2> length(binary_combinations(3))
+%%     8
+-spec binary_combinations(NBits :: pos_integer()) -> [list(boolean())].
+
+binary_combinations(NBits) ->
+    product(lists:duplicate(NBits, [true, false])).
+
+
+%% @doc combinations(N, Items).
+%% Generate all combinations by choosing N values from a given list of Items
+%% in sorted order. Each combination is sorted and the entire table is sorted.
+%% For example:
+%%   1> couch_tests_combinatorics:n_combinations(2, [mon, tue, wed, thu, fri]).
+%%      [
+%%       [mon, tue],
+%%       [mon, wed],
+%%       [mon, thu],
+%%       [mon, fri],
+%%       [tue, wed],
+%%       [tue, thu],
+%%       [tue, fri],
+%%       [wed, thu],
+%%       [wed, fri],
+%%       [thu, fri]
+%%      ]
+-spec n_combinations(Size :: pos_integer(), Elements :: list()) -> [list()].
+
+n_combinations(0, _) ->
+    [[]];
+n_combinations(_, []) ->
+    [];
+n_combinations(N, [H | T]) ->
+    [[H | L] || L <- n_combinations(N - 1, T)] ++ n_combinations(N, T).