docs: include test dependency and random test information

[alestiago]

Includes two new practices:

• Do not share state between tests
• Use random test ordering

[jsgalarraga]

Solid content, just 2 comments

[alestiago]

Running the formatter (npm run format) messes with the actual expected result, introducing unintended characters and providing wrong indentation, for example it results on:

group(\_Counter, () {
late \_Counter counter;

I'm currently not quite sure what's causing such behavior but it's a consequence of applying @jsgalarraga suggestion on #64 (comment).

[alestiago]

Formatting has now been resolved, it seems that new lines are needed to avoid the formatter having unexpected brain seizures results.

[alestiago]

@marwfair @jolexxa, since @jsgalarraga approved, it can now be merged. However, I'll wait until I hear feedback from either of you before merging these practices in.

[marwfair]

LGTM!

[alestiago]

@jolexxa I need a re-review from you here since your requested changes are blocking the effort from being merged in.