Add unit tests for Utils::toHex

platformio.ini

@@ -151,3 +151,17 @@ lib_deps =
   stevemarple/MicroNMEA @ ^2.0.6
   adafruit/Adafruit BME680 Library @ ^2.0.4
   adafruit/Adafruit BMP085 Library @ ^1.2.4
+
+; ----------------- TESTING ---------------------
+
+[env:native]
+platform = native
+build_flags = -std=c++14
+  -I src
+  -I test/mocks
+test_build_src = yes
+build_src_filter =
+  -<*>
+  +<../src/Utils.cpp>
+lib_deps =
+  google/googletest @ ^1.15.2