Add some tests

[astrojuanlu]

You are doing a great job with the pull requests and the reviews. However, without looking closely at the code it's clear that there's a lot of functionality, but it's not tested. I recommend you to

• Test what has already been implemented
• Do not include further functionality if it's not tested

Otherwise, it's very common to leave the tests for the end, and believe me - you will find unexpected problems!