[Feature] Better incremental test with full-expect

[DamienBoue]

Is this your first time submitting a feature request?

• [X] I have read the expectations for open source contributors
• [X] I have searched the existing issues, and I could not find an existing issue for this feature
• [X] I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

Describe the feature

When we use incremental tests we are not able to test if the merge happen correctly.

Ex:

• I have 2 elements already calculated, A and B
• I need to add one element C and to modify the old element A
• I want to test that my incremental test has only 3 elements, A B and C, with B that has been modified and not duplicated

One solution would be to let us test a full-expect that can test the integrality of the data present after the increment.

This could be written as follow:

expect:
  full_mode: true
  rows:
    - { all the rows }

This would permit us to have non regression test on which someone break the unique key where the merge is done.

Describe alternatives you've considered

No response

Who will this benefit?

Everyone who intent to make non regression tests in the application

Are you interested in contributing this feature?

No response

Anything else?

No response