test: Assumeutxo: import snapshot in a node with a divergent chain

[alfonsoromanz]

This PR adds tests to cover two scenarios of loading a snapshot when the current chain tip is:

• Not an ancestor of the snapshot block but has less work
• Not an ancestor or a descendant of the snapshot block and has more work

In the second scenario, the snapshot block does not belong to the most-work chain anymore so I believe it covers this scenario too: TODO: Valid snapshot file and snapshot block, but the block is not on the most-work chain. Therefore I deleted that TODO as well.

[DrahtBot]

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage

For detailed information about the code coverage, see the test coverage report.

Reviews

See the guideline for information on the review process.

Type	Reviewers
Concept ACK	naiyoma
Stale ACK	rkrux

If your review is incorrectly listed, please react with 👎 to this comment and the bot will ignore it on the next update.

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #30053 (test: added test coverage to loadtxoutset could not open file by kevkevinpal)
• #29681 (test: loading assumeutxo snapshot start states by BrandonOdiwuor)
• #29428 (test: Assumeutxo: snapshots with less work should not be loaded by hernanmarino)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[alfonsoromanz]

I splitted the original commit into two commits (one for each test). The second test (af0f401) may be redundant with this one: #29428. The only difference is that my test is executed on a node that has a divergent chain after block 199. I did that to cover this scenario described in the comments

[...] Loading a snapshot when the current chain tip is: [...] Not an ancestor or a descendant of the snapshot block and has more work

If it's redundant I can delete the second commit. Thoughts?

[naiyoma]

Concept ACK, covers more tests scenarios for AssumeUTXO

[rkrux]

tACK ce80f7e

Make and tests successful, thanks for adding this test - it's easy to follow through.

[alfonsoromanz]

Rebased. I also addressed some feedback from rkrux's comments: changed hardcoded value of nblocks from 99 to a dynamic value, i.e SNAPSHOT_BASE_HEIGHT-START_HEIGHT-1

[naiyoma]

Test passes for all three scenarios:

• a7501f7 loading a snapshot when chain tip isn't ancestor but has less work
• 3f03354 loading a snapshot when chain tip isn't ancestor/descendant, has more work and A valid snapshot file & snapshot block, but the block is not on the most-work chain

[naiyoma]

I splitted the original commit into two commits (one for each test). The second test (af0f401) may be redundant with this one: #29428. The only difference is that my test is executed on a node that has a divergent chain after block 199. I did that to cover this scenario described in the comments

[...] Loading a snapshot when the current chain tip is: [...] Not an ancestor or a descendant of the snapshot block and has more work

If it's redundant I can delete the second commit. Thoughts?

IMO you should not delete the second commit, both tests verify that the snapshot load fails but under different scenarios