Removed some redundant tests from "mean_substract_transform".
Removed some redundant tests from "mean_substract_transform".

* One test should test one thing. This should be a general principle. In
  the tests for functions "code" and "decode" we also retested things
  tested for in the constructor test. I've removed this and now we have
  some simpler tests. This holds especially since we reuse data and code
  in successive tests.

horia141/masters-thesis,horia141/masters-thesis