Add more tests

[andreventuravale]

This repository is great and I'm using it myself.

But I feel it would be better to have more tests, with different scenarios, so that the project would increase in reliability.

Tests that would be good:

• Tests for different versions of webpack;
• Edge cases;

Please let me know if I can help.

[plasticine]

Hey there @andreventuravale,

Check out the integration tests, they do some broad checks of different webpack versions (1, 2, 3 &4).

As for edge-cases, I’m always open to PRs failing that individual issues for any specific issues. :)