- Extract the json reading from the json merging: it makes the code hard to understand.
This helps for the separation of concerns: the jsons are read in one method;
and merged in a second one
- Added a first test to check the merge function
No change in behaviour was done, this change is just there to increase code coverage
and to prepare for #9315
Integration tests are useful in detecting breakages but much slower so
let's only use one per command and install formula outside the
integration test framework (which is also slow).
