diff --git a/include/fluent_tray.hpp b/include/fluent_tray.hpp
index 234f2d4..c3a53ee 100644
--- a/include/fluent_tray.hpp
+++ b/include/fluent_tray.hpp
@@ -75,6 +75,10 @@ typedef enum {
 #include <string>
 #include <vector>
 
+#if defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wold-style-cast"
+#endif
+
 
 /**
  * @namespace fluent_tray
@@ -191,8 +195,8 @@ namespace fluent_tray
             static constexpr auto bits = type2bit<OutType>() ;
             static const auto lower_mask = util::bit2mask(bits) ;
 
-            upper = static_cast<OutType>(reinterpret_cast<std::size_t>(input) >> bits) ;
-            lower = static_cast<OutType>(reinterpret_cast<std::size_t>(input) & lower_mask) ;
+            upper = static_cast<OutType>((std::size_t)(input) >> bits) ;
+            lower = static_cast<OutType>((std::size_t)(input) & lower_mask) ;
         }
 
         /**
@@ -209,7 +213,7 @@ namespace fluent_tray
 
             auto out_upper = static_cast<std::size_t>(upper) << bits ;
             auto out_lower = static_cast<std::size_t>(lower) & lower_mask ;
-            out = reinterpret_cast<OutType>(out_upper | out_lower) ;
+            out = (OutType)(out_upper | out_lower) ;
         }
         /**
          * @brief Calculate grayscale value from RGB
@@ -1685,4 +1689,8 @@ namespace fluent_tray
     unsigned int FluentTray::message_id_ ;
 }
 
+#if defined(__GNUC__)
+#pragma GCC diagnostic warning "-Wold-style-cast"
+#endif
+
 #endif
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 931de3a..0d9990b 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -88,9 +88,11 @@ function(AddTest TEST_NAME)
     )
 endfunction()
 
-AddTest(string_test string_test.cpp)
-AddTest(menu_test menu_test.cpp)
-AddTest(tray_test tray_test.cpp)
+AddTest(test_string test_string.cpp)
+AddTest(test_menu test_menu.cpp)
+AddTest(test_tray test_tray.cpp)
+AddTest(test_bits test_bits.cpp)
+AddTest(test_color test_color.cpp)
 
 set(
     CMAKE_CTEST_ARGUMENTS
diff --git a/tests/test_bits.cpp b/tests/test_bits.cpp
new file mode 100644
index 0000000..0185da7
--- /dev/null
+++ b/tests/test_bits.cpp
@@ -0,0 +1,65 @@
+#include "test.hpp"
+
+using namespace fluent_tray ;
+
+
+TEST_CASE("Bits test: ") {
+    SUBCASE("bit2mask") {
+        CHECK_EQ(util::bit2mask(1),                                 0b1) ;
+        CHECK_EQ(util::bit2mask(2),                                0b11) ;
+        CHECK_EQ(util::bit2mask(3),                               0b111) ;
+        CHECK_EQ(util::bit2mask(4),                              0b1111) ;
+        CHECK_EQ(util::bit2mask(5),                             0b11111) ;
+        CHECK_EQ(util::bit2mask(6),                            0b111111) ;
+        CHECK_EQ(util::bit2mask(7),                           0b1111111) ;
+        CHECK_EQ(util::bit2mask(8),                          0b11111111) ;
+        CHECK_EQ(util::bit2mask(9),                         0b111111111) ;
+        CHECK_EQ(util::bit2mask(10),                       0b1111111111) ;
+        CHECK_EQ(util::bit2mask(11),                      0b11111111111) ;
+        CHECK_EQ(util::bit2mask(12),                     0b111111111111) ;
+        CHECK_EQ(util::bit2mask(13),                    0b1111111111111) ;
+        CHECK_EQ(util::bit2mask(14),                   0b11111111111111) ;
+        CHECK_EQ(util::bit2mask(15),                  0b111111111111111) ;
+        CHECK_EQ(util::bit2mask(16),                 0b1111111111111111) ;
+        CHECK_EQ(util::bit2mask(17),                0b11111111111111111) ;
+        CHECK_EQ(util::bit2mask(18),               0b111111111111111111) ;
+        CHECK_EQ(util::bit2mask(19),              0b1111111111111111111) ;
+        CHECK_EQ(util::bit2mask(20),             0b11111111111111111111) ;
+        CHECK_EQ(util::bit2mask(21),            0b111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(22),           0b1111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(23),          0b11111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(24),         0b111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(25),        0b1111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(26),       0b11111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(27),      0b111111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(28),     0b1111111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(29),    0b11111111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(30),   0b111111111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(31),  0b1111111111111111111111111111111) ;
+        CHECK_EQ(util::bit2mask(32), 0b11111111111111111111111111111111) ;
+    }
+
+    SUBCASE("type2bit") {
+        CHECK_EQ(util::type2bit<std::uint32_t>(), 32) ;
+    }
+
+    SUBCASE("split_bits") {
+        std::uint32_t value = 0x11f97892 ;
+        std::uint16_t upper, lower ;
+
+        util::split_bits(value, upper, lower) ;
+
+        CHECK_EQ(upper, 0x11f9) ;
+        CHECK_EQ(lower, 0x7892) ;
+    }
+
+    SUBCASE("concatenate_bits") {
+        std::uint16_t upper = 0x112f ;
+        std::uint16_t lower = 0x88fc ;
+        std::uint32_t value ;
+
+        util::concatenate_bits(upper, lower, value) ;
+
+        CHECK_EQ(value, 0x112f88fc) ;
+    }
+}
diff --git a/tests/test_color.cpp b/tests/test_color.cpp
new file mode 100644
index 0000000..7005d8e
--- /dev/null
+++ b/tests/test_color.cpp
@@ -0,0 +1,9 @@
+#include "test.hpp"
+
+using namespace fluent_tray ;
+
+TEST_CASE("Color test: ") {
+    auto color = RGB(124, 214, 122) ;
+    unsigned char expected_color = 188 ;
+    CHECK_EQ(util::rgb2gray(color), expected_color) ;
+}
diff --git a/tests/menu_test.cpp b/tests/test_menu.cpp
similarity index 100%
rename from tests/menu_test.cpp
rename to tests/test_menu.cpp
diff --git a/tests/string_test.cpp b/tests/test_string.cpp
similarity index 100%
rename from tests/string_test.cpp
rename to tests/test_string.cpp
diff --git a/tests/tray_test.cpp b/tests/test_tray.cpp
similarity index 100%
rename from tests/tray_test.cpp
rename to tests/test_tray.cpp