Run tests against hardware-wallet/skycoin-api

**Feature description**
Refactor tests

**Describe the feature**

It's desired to run this tests battery against [hardware-wallet/skycoin-api](https://github.com/skycoin/hardware-wallet/tree/ffd6fcdaf1d89a0877372f6549cd8a4035a49760/skycoin-api), as hardware-wallet/skycoin-api have a subset of the libskycoin features it's required to refactor the tests to run all against libskycoin as it' currently and a test subset against hardware-wallet/skycoin-api.

**Describe the solution you'd like**
Just refactor tests without changing them.

**Describe alternatives you've considered**
Modifing the library it's not al alternative as this code is auto generated.

**Additional context**
https://github.com/skycoin/hardware-wallet/issues/84

**Possible implementation**
This is just about a refactorization, please do not change any thing