Fix Slerp C# docs and add test cases for vectors in the same direction

modules/mono/glue/GodotSharp/GodotSharp/Core/Vector2.cs

@@ -511,8 +511,9 @@ namespace Godot
         /// Returns the result of the spherical linear interpolation between
         /// this vector and <paramref name="to"/> by amount <paramref name="weight"/>.
         ///
-        /// This method also handles interpolating the lengths if the input vectors have different lengths.
-        /// For the special case of one or both input vectors having zero length, this method behaves like [method lerp].
+        /// This method also handles interpolating the lengths if the input vectors
+        /// have different lengths. For the special case of one or both input vectors
+        /// having zero length, this method behaves like <see cref="Lerp"/>.
         /// </summary>
         /// <param name="to">The destination vector for interpolation.</param>
         /// <param name="weight">A value on the range of 0.0 to 1.0, representing the amount of interpolation.</param>

modules/mono/glue/GodotSharp/GodotSharp/Core/Vector3.cs

@@ -551,8 +551,9 @@ namespace Godot
         /// Returns the result of the spherical linear interpolation between
         /// this vector and <paramref name="to"/> by amount <paramref name="weight"/>.
         ///
-        /// This method also handles interpolating the lengths if the input vectors have different lengths.
-        /// For the special case of one or both input vectors having zero length, this method behaves like [method lerp].
+        /// This method also handles interpolating the lengths if the input vectors
+        /// have different lengths. For the special case of one or both input vectors
+        /// having zero length, this method behaves like <see cref="Lerp"/>.
         /// </summary>
         /// <param name="to">The destination vector for interpolation.</param>
         /// <param name="weight">A value on the range of 0.0 to 1.0, representing the amount of interpolation.</param>

tests/core/math/test_vector2.h

@@ -89,6 +89,9 @@ TEST_CASE("[Vector2] Interpolation methods") {
 	CHECK_MESSAGE(
 			Vector2(5, 0).slerp(Vector2(0, 5), 0.5).is_equal_approx(Vector2(5, 5) * Math_SQRT12),
 			"Vector2 slerp with non-normalized values should work as expected.");
+	CHECK_MESSAGE(
+			Vector2(1, 1).slerp(Vector2(2, 2), 0.5).is_equal_approx(Vector2(1.5, 1.5)),
+			"Vector2 slerp with colinear inputs should behave as expected.");
 	CHECK_MESSAGE(
 			Vector2().slerp(Vector2(), 0.5) == Vector2(),
 			"Vector2 slerp with both inputs as zero vectors should return a zero vector.");

tests/core/math/test_vector3.h

@@ -110,6 +110,9 @@ TEST_CASE("[Vector3] Interpolation methods") {
 	CHECK_MESSAGE(
 			Vector3(5, 0, 0).slerp(Vector3(0, 3, 4), 0.5).is_equal_approx(Vector3(3.535533905029296875, 2.121320486068725586, 2.828427314758300781)),
 			"Vector3 slerp with non-normalized values should work as expected.");
+	CHECK_MESSAGE(
+			Vector3(1, 1, 1).slerp(Vector3(2, 2, 2), 0.5).is_equal_approx(Vector3(1.5, 1.5, 1.5)),
+			"Vector3 slerp with colinear inputs should behave as expected.");
 	CHECK_MESSAGE(
 			Vector3().slerp(Vector3(), 0.5) == Vector3(),
 			"Vector3 slerp with both inputs as zero vectors should return a zero vector.");