Unit tests for TERingStack

[aregtech]

Description:
TERingStack is a Ring Stack. It is needed to add unit tests to test all public methods and to cover as much codes as possible.

Solution:

1. There is a ./tests/units/ folder in the project to add unit tests.
2. Add in that folder a new unit testing file, for example TERingStack.cpp, and write unit tests.
   • The unit tests should run at least with int, unsigned int, float / double and std::string and String / WideString types.
   • The tests with the custom types, like custom structures, are welcome, but it is optional.
   • If the amount of testing methods are to large, they can be split and can be implemented either in a separate folder (for example array) or can be split to separate files like TERingStackStringTest.cpp.
   • Each created file should be added in the CMakeLists.txt and in the areg-tests MSVC project.
   • Each .cpp file should have a list of tested methods at the top
   • Each test method should have convenient name that is describing the purpose of the test, and should have short description.
3. The tests should run. In case if a bug found, create a ticket and mention the priority in the title, like [bug]. Each created ticket should have at least 2 labels: bug and unit test.