Use friend class instead of protected members.

The reference got cluttered after I changed the private members to
protected.

src/identiconpp.hpp

@@ -42,6 +42,7 @@ using std::array;
 class Identiconpp
 {
 public:
+    friend class Testiconpp;
     /*!
      * @brief  List of identicon algorithms
      */
@@ -89,7 +90,7 @@ public:
      */
     Magick::Image generate(const string &digest, const uint16_t width = 100);
 
-protected:
+private:
     const uint8_t _rows;
     const uint8_t _columns;
     const algorithm _type;

src/tests/test_checks_entropy.cpp

@@ -6,7 +6,7 @@
 
 using std::string;
 
-class Testiconpp : protected Identiconpp
+class Testiconpp : private Identiconpp
 {
 public:
     explicit Testiconpp(const uint8_t columns, const uint8_t rows,

src/tests/test_checks_hex.cpp

@@ -6,7 +6,7 @@
 
 using std::string;
 
-class Testiconpp : protected Identiconpp
+class Testiconpp : private Identiconpp
 {
 public:
     explicit Testiconpp()