[WIP] test: Fix reorg patterns in mempool tests to use proper fork-based approach #32587

1. 
   i-am-yuvi commented at 1:26 pm on May 22, 2025: contributor

   Addresses #32531

   This is a Work In Progress, not ready for review yet.

   Currently updating functional tests to replace direct use of invalidateblock with proper fork-based reorg behaviour. The direct invalidation approach bypasses important validation checks and has depth limitations(10 block) that don’t match real-world reorg scenarios.

   Plan:

   • Fix mempool_ephemeral_dust.py reorg patterns
   • Audit and fix other mempool_*.py tests
   • Update any additional tests using problematic reorg patterns

   Will mark ready for review once all functional tests are updated and verified.

2. 
   DrahtBot commented at 1:26 pm on May 22, 2025: contributor

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

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32587.

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #32468 (rpc: generatetomany by polespinasa)

   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.

3. 
   instagibbs commented at 1:27 pm on May 22, 2025: member

   feel free to ping me when it’s ready
4. 
   i-am-yuvi commented at 1:30 pm on May 22, 2025: contributor

   feel free to ping me when it’s ready

   Sure!

5. fix: reorg behaviour in mempool tests

   The current test directly uses invalidatblock to trigger
   mempool re-entry of transactions. Unfortunately, the
   behavior doesn't match what a real reorg would look like. As
   a result you get surprising behavior such as the mempool
   descendant chain limits being exceeded, or if a fork is
   greater than 10 blocks deep, evicted block transactions stop
   being submitted back into in the mempool.
   
   Fix this by preparing an empty fork chain, invalidating that
   via rpc, and then continuing with the logic, finally
   reconsidering the fork chain once the rest of the test is
   prepared. This triggers a more typical codepath.
   
   see https://github.com/bitcoin/bitcoin/pull/32516/commits/2b202e9db56487e658fc41089178f31ef4259a0d

   79caa92ca9
6. i-am-yuvi force-pushed on May 23, 2025

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