Unit test for ranget drop and skip

This tests that these operations behave as expected and gives examples
on how to use them.

Author: romainbrenguier

unit/util/range.cpp

@@ -57,6 +57,45 @@ SCENARIO("range tests", "[core][util][range]")
       ++it;
       REQUIRE(it == filtered_range.end());
     }
+    THEN("Drop first 2 elements")
+    {
+      auto range = make_range(list);
+      const bool elements_left = range.drop(2);
+      REQUIRE(elements_left);
+      auto it = range.begin();
+      REQUIRE(*it == "acdef");
+      const bool more_elements_left = range.drop(1);
+      REQUIRE(!more_elements_left);
+      REQUIRE(range.empty());
+    }
+    THEN("Drop first 5 elements")
+    {
+      auto range = make_range(list);
+      const bool elements_left = range.drop(5);
+      REQUIRE(!elements_left);
+      REQUIRE(range.empty());
+    }
+    THEN("Skip first 2 elements")
+    {
+      auto range = make_range(list);
+      auto skip_range = range.skip(2);
+      auto it = skip_range.begin();
+      REQUIRE(*it == "acdef");
+      skip_range.drop(1);
+      REQUIRE(skip_range.empty());
+      // Check the original is unmodified
+      REQUIRE(!range.empty());
+      REQUIRE(*range.begin() == "abc");
+    }
+    THEN("Skip first 5 elements")
+    {
+      auto range = make_range(list);
+      auto skip_range = range.skip(5);
+      REQUIRE(skip_range.empty());
+      // Check the original is unmodified
+      REQUIRE(!range.empty());
+      REQUIRE(*range.begin() == "abc");
+    }
     THEN(
       "A const instance of a `filter_iteratort` can mutate the input "
       "collection.")