test: Move tx creation to create_self_transfer_multi #26414

Two birds with one stone: replacement of #26278 with simplification of the MiniWallet's transaction creation logic.

Currently the MiniWallet creates simple txns (1 input, 1 output) with create_self_transfer. #24637 introduced create_self_transfer_multi which uses create_self_transfer to create a "transaction template" which then adjusts (copy and mutate inputs and outputs) in order to create more complex multi-input multi-output transactions. This can more easily lead to issues such as #26278 and is more of a maintenance burden.

This PR simplifies the logic by going the other way around. Now create_self_transfer uses create_self_transfer_multi. The transaction creation logic has been moved to create_self_transfer_multi which is being called by create_self_transfer to construct the simple case of 1 input 1 output transaction.

Concept ACK. It looks cleaner and, as you said, simplified, I'll take a deeper look soon.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #26625 (test: Run mempool_packages.py with MiniWallet by MarcoFalke)
• #25038 (policy: nVersion=3 and Package RBF by glozow)
• #20892 (tests: Run both descriptor and legacy tests within a single test invocation by achow101)

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.

Code Review ACK. At first sight, everything looks fine. @kouloumos did you have a chance to test the output of these functions before / after the change? Something interesting to try would be to verify the output of the previous/current version of each pair of functions, but I didn't have a chance to do it yet.

[...] did you have a chance to test the output of these functions before / after the change? Something interesting to try would be to verify the output of the previous/current version of each pair of functions, but I didn't have a chance to do it yet. @hernanmarino I'm not sure if I understood what you are trying to say. The individual tests that are using those functions are working properly, which means that the output is the same.

@hernanmarino I'm not sure if I understood what you are trying to say. The individual tests that are using those functions are working properly, which means that the output is the same.

At the moment of my comment I had an idea of doing myself some other tests, but now I have a deeper understanding of the changes, and it looks ok. And as you say, if the tests work, there is no reason to do anything else.

ACK 0b78110f73965fd827748107e0f3497d3352be71 👒

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