Add comprehensive tests for kf::views::adjacent and kf::views::pairwise (#25)

* Initial plan

* Add comprehensive tests for kf::views::adjacent and kf::views::pairwise

Co-authored-by: SergiusTheBest <4660722+SergiusTheBest@users.noreply.github.com>

* Address PR feedback: Remove std::vector usage and add tests for large adjacent windows

Co-authored-by: SergiusTheBest <4660722+SergiusTheBest@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: SergiusTheBest <4660722+SergiusTheBest@users.noreply.github.com>

Author: Copilot

test/AdjacentView.cpp

@@ -30,5 +30,128 @@ SCENARIO("views::adjacent")
                 REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
             }
         }
+
+        WHEN("create adjacent view for 3 elements")
+        {
+            auto view = arr | kf::views::adjacent<3>;
+
+            THEN("view contains 2 tuples: (1,2,3)(2,3,4)")
+            {
+                std::array<std::tuple<int, int, int>, 2> expected = { { {1, 2, 3}, {2, 3, 4} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+
+        WHEN("create adjacent view for 4 elements")
+        {
+            auto view = arr | kf::views::adjacent<4>;
+
+            THEN("view contains 1 tuple: (1,2,3,4)")
+            {
+                std::array<std::tuple<int, int, int, int>, 1> expected = { { {1, 2, 3, 4} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+    }
+}
+
+SCENARIO("views::pairwise")
+{
+    GIVEN("array with 5 elements: 10,20,30,40,50")
+    {
+        std::array<int, 5> arr = { 10, 20, 30, 40, 50 };
+
+        WHEN("create pairwise view")
+        {
+            auto view = arr | kf::views::pairwise;
+
+            THEN("view contains 4 pairs: (10,20)(20,30)(30,40)(40,50)")
+            {
+                std::array<std::tuple<int, int>, 4> expected = { { {10, 20}, {20, 30}, {30, 40}, {40, 50} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+    }
+}
+
+SCENARIO("views::adjacent edge cases")
+{
+    GIVEN("array with 1 element: 42")
+    {
+        std::array<int, 1> arr = { 42 };
+
+        WHEN("create adjacent view for 1 element")
+        {
+            auto view = arr | kf::views::adjacent<1>;
+
+            THEN("view contains 1 tuple: (42)")
+            {
+                std::array<std::tuple<int>, 1> expected = { { {42} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+    }
+
+    GIVEN("array with 2 elements: 5,7")
+    {
+        std::array<int, 2> arr = { 5, 7 };
+
+        WHEN("create adjacent view for 2 elements")
+        {
+            auto view = arr | kf::views::adjacent<2>;
+
+            THEN("view contains 1 tuple: (5,7)")
+            {
+                std::array<std::tuple<int, int>, 1> expected = { { {5, 7} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+
+        WHEN("create pairwise view")
+        {
+            auto view = arr | kf::views::pairwise;
+
+            THEN("view contains 1 pair: (5,7)")
+            {
+                std::array<std::tuple<int, int>, 1> expected = { { {5, 7} } };
+
+                REQUIRE(std::equal(view.begin(), view.end(), expected.begin(), expected.end()));
+            }
+        }
+    }
+
+    GIVEN("array with 2 elements but adjacent window of 3")
+    {
+        std::array<int, 2> arr = { 10, 20 };
+
+        WHEN("create adjacent view for 3 elements")
+        {
+            auto view = arr | kf::views::adjacent<3>;
+
+            THEN("view is empty since window is larger than input")
+            {
+                REQUIRE(view.begin() == view.end());
+            }
+        }
+    }
+
+    GIVEN("array with 1 element but adjacent window of 2")
+    {
+        std::array<int, 1> arr = { 99 };
+
+        WHEN("create pairwise view")
+        {
+            auto view = arr | kf::views::pairwise;
+
+            THEN("view is empty since window is larger than input")
+            {
+                REQUIRE(view.begin() == view.end());
+            }
+        }
     }
 }