Decouple unit tests from db/filesystem

[katcipis]

Right now we have tests that are coupled with databases and the filesystem.

[i4ki]

I don't have an idea in a manner to solve that problem.

An index is made of N databases of reverse indices, where N is the number of document's field. Today, when we create a new index, the first step is creating a directory on filesystem to hold that databases inside... And when the instance *index.Index is created we need to create a file for store the index's metadata (info.json).

In the case of KV store implementations (leveldb, rocksdb, etc) we can mock the KVStore interface to hold data in-memory, but for the case of index creation above I don't see a good option.

Of course, we can rethink the current implementation. Do you have any idea in mind?

We have a lot of mess with the current way of doing unit tests, and I agree that we need a better way to do that.

[katcipis]

Actually, if we pretend to rewrite stuff the best kind of tests to write right now will be integration tests. This way we will be able to refactor with a little more safety :-). I will focus on this right now

[i4ki]

https://github.com/tsuru/tsuru/blob/master/fs/filesystem.go

[katcipis]

@tiago4orion Your idea is to define a filesystem interface and use it ? So we can mock it on the tests ? If this is the idea...I like it :-)