Add more tests for chunk generation function

app/es_subset_generator/test/test_utils_functions.py

@@ -17,12 +17,11 @@ class TestUtilFunctions(unittest.TestCase):
         """
         list_size = 100
         original_list = list(range(0, list_size))
-        original_list_size = len(original_list)
 
         for chunk_size in range(1, list_size + 10):
             chunks_obtained = list(utils.get_list_chunks(chunk_size, original_list))
             total_size_obtained = sum([len(chunk) for chunk in chunks_obtained])
-            self.assertTrue(total_size_obtained == original_list_size,
+            self.assertTrue(total_size_obtained == list_size,
                             msg='The total size of the chunks do not match the size of the original list!')
 
             items_found = set()
@@ -33,3 +32,26 @@ class TestUtilFunctions(unittest.TestCase):
 
             for item in original_list:
                 self.assertIn(item, items_found, msg=f'The item {item} is missing in the chunks!')
+
+    def test_list_chunk_fails_with_nonsense_numbers(self):
+        """
+        Tests that the chunks function fails when nonsense numbers are given (negative and zero)
+        """
+
+        list_size = 100
+        original_list = list(range(0, list_size))
+
+        with self.assertRaises(utils.ChunkSizeNonSenseError,
+                               msg='It should raise an error with a nonsense chunk size!'):
+            utils.get_list_chunks(0, original_list)
+            utils.get_list_chunks(-1, original_list)
+
+    def test_list_chunk_works_with_empty_list(self):
+        """
+        test chunks function works with an empty list. It should create an empty chunk list
+        """
+        list_size = 0
+        original_list = list(range(0, list_size))
+
+        chunks_obtained = list(utils.get_list_chunks(10, original_list))
+        self.assertEqual(chunks_obtained, [], msg=f'No chunks must have been produced!')

app/es_subset_generator/utils.py

@@ -3,12 +3,35 @@ Utils functions for handling the subset creation
 """
 
 
+class ChunkSizeNonSenseError(Exception):
+    """
+    Error raised when the chunk size does not make sense
+    """
+
+
 def get_list_chunks(chunk_size, original_list):
     """
     :param chunk_size: size of chunk to obtain
     :param original_list: list to split
     :return: a generator object with the chunks of the original list with the given size
     """
+    if chunk_size <= 0:
+        raise ChunkSizeNonSenseError(f'A chunk size of {chunk_size} does not make sense!')
+
+    if len(original_list) == 0:
+        return []
+
+    return prepare_list_chunks_generator(chunk_size, original_list)
+
+
+def prepare_list_chunks_generator(chunk_size, original_list):
+    """
+    Prepares the generator to get the list chunks
+    :param chunk_size: size of chunk to obta
+    :param original_list: list to split
+    :return: a generator object with the chunks of the original list with the given size
+    """
+
     start_index = 0
     end_index = chunk_size
     original_list_size = len(original_list)