Mock planner in tests

[csegarragonz]

In this PR we bump the faabric tag to include the planner mocking in the tests.

In practice, we only need to modify a couple of test cases to include the right planner test fixture.

[codecov]

Codecov Report

Merging #761 (b7a4886) into main (850730c) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #761      +/-   ##
==========================================
- Coverage   67.40%   67.38%   -0.03%     
==========================================
  Files          69       69              
  Lines        7726     7726              
==========================================
- Hits         5208     5206       -2     
- Misses       2518     2520       +2     

see 2 files with indirect coverage changes