Add tests

[ghost]

I have some tests in the code but isn't enough.

For that and taking advantage that this month is Hacktoberfest. 😄
I purpose you to add some tests, not in all the code, be can move forward with the list or another thing if you have any suggestion.

We can start with:

• Check the test/utils that already exists and add more or improve those.
• Write a test for shared/formats.
• Write a test for decorators/ resize.
• Write tests for entire components unit and e2e.

[peterennis]

@edgarordonez

I recommend closing this and creating a new one for D3-Stencil v2.0.0
based on this PR: #43
in connection to these test results.