Added more unittest coverage

Added Mutex for gmtime functions
Moved Statics used in ClockCommon to ClockCommon

src/fsfw/timemanager/Clock.h

@@ -173,6 +173,7 @@ class Clock {
 
   static MutexIF *timeMutex;
   static uint16_t leapSeconds;
+  static bool leapSecondsSet;
 };
 
 #endif /* FSFW_TIMEMANAGER_CLOCK_H_ */

src/fsfw/timemanager/ClockCommon.cpp

@@ -3,6 +3,10 @@
 #include "fsfw/ipc/MutexGuard.h"
 #include "fsfw/timemanager/Clock.h"
 
+uint16_t Clock::leapSeconds = 0;
+MutexIF* Clock::timeMutex = nullptr;
+bool Clock::leapSecondsSet = false;
+
 ReturnValue_t Clock::convertUTCToTT(timeval utc, timeval* tt) {
   uint16_t leapSeconds;
   ReturnValue_t result = getLeapSeconds(&leapSeconds);
@@ -29,12 +33,16 @@ ReturnValue_t Clock::setLeapSeconds(const uint16_t leapSeconds_) {
   MutexGuard helper(timeMutex);
 
   leapSeconds = leapSeconds_;
+  leapSecondsSet = true;
 
   return HasReturnvaluesIF::RETURN_OK;
 }
 
 ReturnValue_t Clock::getLeapSeconds(uint16_t* leapSeconds_) {
-  if (timeMutex == nullptr) {
+  if(not leapSecondsSet){
+    return HasReturnvaluesIF::RETURN_FAILED;
+  }
+  if (checkOrCreateClockMutex() != HasReturnvaluesIF::RETURN_OK) {
     return HasReturnvaluesIF::RETURN_FAILED;
   }
   MutexGuard helper(timeMutex);
@@ -49,6 +57,13 @@ ReturnValue_t Clock::convertTimevalToTimeOfDay(const timeval* from, TimeOfDay_t*
   // According to https://en.cppreference.com/w/c/chrono/gmtime, the implementation of gmtime_s
   // in the Windows CRT is incompatible with the C standard but this should not be an issue for
   // this implementation
+  ReturnValue_t result = checkOrCreateClockMutex();
+  if(result != HasReturnvaluesIF::RETURN_OK){
+    return result;
+  }
+  MutexGuard helper(timeMutex);
+  // gmtime writes its output in a global buffer which is not Thread Safe
+  // Therefore we have to use a Mutex here
   timeInfo = gmtime(&from->tv_sec);
   to->year = timeInfo->tm_year + 1900;
   to->month = timeInfo->tm_mon + 1;