increase code coverage

[simoneb]

as titled

[mcollina]

This is not finished:

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |      100 |    96.08 |      100 |      100 |                   |
 index.js |      100 |    96.08 |      100 |      100 |   226,233,349,491 |
----------|----------|----------|----------|----------|-------------------|