diff --git a/tests/validation/ReferenceCPP.h b/tests/validation/ReferenceCPP.h
index 4173b8b..b5e3fa0 100644
--- a/tests/validation/ReferenceCPP.h
+++ b/tests/validation/ReferenceCPP.h
@@ -42,6 +42,26 @@
 class ReferenceCPP final : public Reference
 {
 public:
+    /** Function to compute reference sobel 3x3.
+     *
+     * @param[in] src                   Input tensor.
+     * @param[in] dst_x                 Result tensor along x axis
+     * @param[in] dst_y                 Result tensor along y axis
+     * @param[in] border_mode           Border mode to use for input tensor
+     * @param[in] constant_border_value Constant value to use if @p border_mode is constant
+     *
+     */
+    static void sobel_3x3(RawTensor &src, RawTensor &dst_x, RawTensor &dst_y, BorderMode border_mode, uint8_t constant_border_value);
+    /** Function to compute reference sobel 5x5.
+     *
+     * @param[in] src                   Input tensor.
+     * @param[in] dst_x                 Result tensor along x axis
+     * @param[in] dst_y                 Result tensor along y axis
+     * @param[in] border_mode           Border mode to use for input tensor
+     * @param[in] constant_border_value Constant value to use if @p border_mode is constant
+     *
+     */
+    static void sobel_5x5(RawTensor &src, RawTensor &dst_x, RawTensor &dst_y, BorderMode border_mode, uint8_t constant_border_value);
     /** Function to compute the mean and standard deviation of a tensor.
      *
      * @param[in]  src     Input tensor.