Adding unit tests for sorting functions, and improving readability on some sorting algorithms (#784)

* Adding variable to fade out ambiguity

* More readability on merge sorting algorithm

* Updating merge_sort_fastest description and explaining why

* Adding tests file with imports

* Standardazing filenames and function names

* Adding test cases and test functions

* Adding test loop

* Putting 'user oriented code' inside main condition for having valid imports

* Fixing condition

* Updating tests: adding cases and todo list

* Refactoring first euler problem's first solution

sorts/tests.py

@@ -0,0 +1,74 @@
+from bogo_sort import bogo_sort
+from bubble_sort import bubble_sort
+from bucket_sort import bucket_sort
+from cocktail_shaker_sort import cocktail_shaker_sort
+from comb_sort import comb_sort
+from counting_sort import counting_sort
+from cycle_sort import cycle_sort
+from gnome_sort import gnome_sort
+from heap_sort import heap_sort
+from insertion_sort import insertion_sort
+from merge_sort_fastest import merge_sort as merge_sort_fastest
+from merge_sort import merge_sort
+from pancake_sort import pancake_sort
+from quick_sort_3_partition import quick_sort_3partition
+from quick_sort import quick_sort
+from radix_sort import radix_sort
+from random_pivot_quick_sort import quick_sort_random
+from selection_sort import selection_sort
+from shell_sort import shell_sort
+from tim_sort import tim_sort
+from topological_sort import topological_sort
+from tree_sort import tree_sort
+from wiggle_sort import wiggle_sort
+
+
+TEST_CASES = [
+    {'input': [8, 7, 6, 5, 4, 3, -2, -5], 'expected': [-5, -2, 3, 4, 5, 6, 7, 8]},
+    {'input': [-5, -2, 3, 4, 5, 6, 7, 8], 'expected': [-5, -2, 3, 4, 5, 6, 7, 8]},
+    {'input': [5, 6, 1, 4, 0, 1, -2, -5, 3, 7], 'expected': [-5, -2, 0, 1, 1, 3, 4, 5, 6, 7]},
+    {'input': [2, -2], 'expected': [-2, 2]},
+    {'input': [1], 'expected': [1]},
+    {'input': [], 'expected': []},
+]
+
+'''
+    TODO:
+    - Fix some broken tests in particular cases (as [] for example),
+    - Unify the input format: should always be function(input_collection) (no additional args)
+    - Unify the output format: should always be a collection instead of updating input elements
+      and returning None
+    - Rewrite some algorithms in function format (in case there is no function definition)
+'''
+
+TEST_FUNCTIONS = [
+    bogo_sort,
+    bubble_sort,
+    bucket_sort,
+    cocktail_shaker_sort,
+    comb_sort,
+    counting_sort,
+    cycle_sort,
+    gnome_sort,
+    heap_sort,
+    insertion_sort,
+    merge_sort_fastest,
+    merge_sort,
+    pancake_sort,
+    quick_sort_3partition,
+    quick_sort,
+    radix_sort,
+    quick_sort_random,
+    selection_sort,
+    shell_sort,
+    tim_sort,
+    topological_sort,
+    tree_sort,
+    wiggle_sort,
+]
+
+
+for function in TEST_FUNCTIONS:
+    for case in TEST_CASES:
+        result = function(case['input'])
+        assert result  == case['expected'], 'Executed function: {}, {} != {}'.format(function.__name__, result, case['expected'])