Improve small details in specs:

* Fix coding standards;
* Simplify some expectations (eq instead of be matcher);
* Expect identity on block instead of calling;
* Change some before call as oneliners;
* Avoid shadowing variable names;
* Improve wording where needed.

spec/support/tests_helpers.rb

@@ -1,9 +1,9 @@
 module TestsHelpers
   def test_ok
-    double('test', pass?: true)
+    double 'test', pass?: true
   end
 
   def test_ko
-    double('test', pass?: false)
+    double 'test', pass?: false
   end
 end