This class is included in net-ssh, but net-sftp adds some new methods
that we need for our tests. This code resides in net-sftp test helper,
and can't be required dynamicaly, this change adds a copy of the code we
need, hardcoded in NetSSHStoryHelpers.
In Condition:
* Modify constructor to accepts tests and a default return value;
* Implement #met?;
* Modify #! so that it return the negated value returned by #met?.
In Condition::DSL:
* Modify .evaluate to build the condition with tests and the value
returned by a the evaluated condition block.
Add a basic Test base class, with env and arguments as attributes.
Add some spec helpers to build some easily testable kind of Test
instances (as test doubles).
