The most important thing is that there is no browser component in his design. This has some interesting ramifications.
- Since you don’t have to spin up browsers, the tests runs are naturally fast.
- Likewise the environment is pure. Only the code you explicitly import into the test engine is in scope, nothing from the browser can leak in.
- Since it is a clean, browserless environment you don’t have access to the DOM or other web-specific objects.
Anatole Tresch Mar 03, 2015