Ask HN: Is there a programming language with embedded testing support?

There are also very few languages that focus on correctness and contracts to help create programs that have fewer bugs. Yet The mayority of languages simply focus on "getting things done", so to speak, and leave testing and correctness out of the picture or add them later on.

Granted, testing support can be added later via libraries and frameworks, but I wonder: in the continuum of program correctness, is there a language that perhaps does not provide full proof/correctness/contract support but does come with testing right out of the box, either in its implementation or philosophy?

Also related question: do you know of any language that was specifically designed to encourage and/or make testing easier for its programs?

Even though I didn't get the "joke" for a recent post about Go[0], I still think it's interesting to ask.

[0] https://news.ycombinator.com/item?id=12371029

https://coq.inria.fr/about-coq

http://www.adacore.com/adaanswers/about/ada-comparison-chart

http://www.adacore.com/gnatpro/toolsuite/utilities/

https://github.com/lampepfl/dotty

http://www.scalatest.org/getting_started_with_feature_spec

http://etorreborre.github.io/specs2/

http://www.gebish.org/

http://spockframework.github.io/spock/docs/1.1-rc-2/introduc...

Its dirt simple to add testing to your project, just create a directory called tests in top level of your project and place rust source files inside them. It then looks for functions inside those files that are annotated as being tests. Similar setup for benchmarks.

Rust also includes generating documentation from comments inside the source code just like doxygen. And it supports embedded examples, which will be checked if those example programs compile at all. It really helps with prevent documentation from going out of date.

All of this is provided from the start when you install rust.