In fact the tolling around Solidity and smart contracts is quite rich. It's possible to write unit tests, execute contracts code on a private chain in a similar way to integration/API tests, and measure the code coverage.

Sadly, it's not a common practice to develop contracts with full use of such tooling. See [0] for an analysis of the recent 2017 ICOs and their use of the tooling in crowdsale contracts. A few gems exist, that do quite thorough testing including a CI approach.

[0] https://medium.com/@bocytko/would-you-trust-your-money-to-a-...