Add unittest

Add unittest
[   31s] + ./version_check
[   31s]
[   31s] running 10 tests
[   31s] test date::tests::display ... ok
[   31s] test tests::test_stable_compatibility ... ok
[   31s] test version::tests::test_comparisons ... ok
[   31s] test version::tests::display ... ok
[   31s] test version::tests::test_from_mmp ... ok
[   31s] test version::tests::test_malformed ... ok
[   31s] test version::tests::test_str_to_mmp ... ok
[   31s] test tests::test_verbose_version_parse ... ok
[   31s] test tests::test_version_parse ... ok
[   31s] test tests::test_parse_current ... ok
[   31s]
[   31s] test result: ok. 10 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.25s