Unit testing is not terra incognita, it's industry best practice. Personally I write at least twice as many lines of code in tests as I do in the implementation under test. That's the nature of test-driven development.

If you doubt that TLS can be tested, may I direct your attention to the extensive suite of unit tests in Go's crypto package. For example http://golang.org/src/pkg/crypto/x509/x509_test.go and http://golang.org/src/pkg/crypto/x509/verify_test.go among many other source files.