Test - Improve unit testing using test helpers library

[titouanfreville]

While working in the repository, it fells quite hard to add clean unit test.

As all tests repose only on golang vanilla tools, it is quite hard to manage tests on Panic for example or provide a clear vue of what is tested, how and why.

Could we envisage to use a library to help assertions and render a clear test output ?

(I am used to https://github.com/smartystreets/goconvey witch outputs can directly be used as doc if correctly written but we could use other solution as well) :)