Added few edge cases to the test suite

tests/test_goulagsort.py

@@ -57,6 +57,17 @@ def test_duplicated_sort():
 
     assert send_to_goulag(inputlist) == expectedList
 
+def test_list_with_zero_and_negatives():
+    inputlist = [0,50,-5,2,-10,7,15]
+    expectedList = sorted(copy.deepcopy(inputlist))
+
+    assert send_to_goulag(inputlist) == expectedList
+
+def test_many_duplicates():
+    input_list = [7, 2, 7, 7, 1, 7, 3, 7]
+    expected_list = sorted(input_list[:])
+    assert send_to_goulag(input_list[:]) == expected_list
+
 def test_really_long_sort():
     inputList = [random.randint(1,500000) for _ in range(10000)]
     expectedList = sorted(copy.deepcopy(inputList))