Added tests to improve code coverage to 100%

[davidribeiro]

Hello,

First time contributing to an open source project, so any tips are welcome!
This is to resolve issue #171
What's being added:

• fix on tests where the output method was being tested (assert doesn't test this method, since the output method doesn't return anything, instead it prints out the command being executed)
• test to check the command executed when process is called with $options
• test the execute with an user (there's an error while executing, may be some problem with docker container)
• test that the execute should throw an exception when the path executable is invalid

[geekcom]

Wooww that's great @davidribeiro thanks so much.

[davidribeiro]

No problem @geekcom, if you need any help just let me know