Add unit tests

CMakeLists.txt

tests/CMakeLists.txt

tests/common-failures_test-case-01.cmake

tests/common-failures_test-case-02.cmake

tests/helpers/assertions.cmake

tests/helpers/test_case_wrapper.cmake

tests/helpers/testee_macro_wrapper.cmake

tests/include-requested-by-common-flag_test-case-01.cmake

tests/include-requested-by-common-flag_test-case-02.cmake

tests/include-requested-by-common-flag_test-case-03.cmake

tests/include-requested-by-common-flag_test-case-04.cmake

tests/include-requested-by-common-flag_test-case-05.cmake

tests/include-requested-by-common-flag_test-case-06.cmake

tests/include-requested-by-common-flag_test-case-07.cmake

tests/include-requested-by-common-flag_test-case-08.cmake

tests/include-requested-by-common-flag_test-case-09.cmake

tests/include-requested-by-common-flag_test-case-10.cmake

tests/include-requested-by-common-flag_test-case-11.cmake

tests/include-requested-by-common-flag_test-case-12.cmake

tests/include-requested-by-component_test-case-01.cmake