tapgarden: harden MockKeyRing and fix flaky queueSeedlingsInBatch test

[ffranr]

This PR makes several changes to stabilize MockKeyRing and reduce test flakiness in queueSeedlingsInBatch:

• Fix incorrect return values in NewMockKeyRing On calls.
• Replace RLock with full mutex locks, always acquired first in each method.
• Add an atomic counter for DeriveNextKey calls to avoid depending on the mock’s mutex.
• Update the test helper to use wait.NoError instead of require.Eventually and relax equality checks to >= expected.

This is the error we're trying to fix (as seen in a recent CI run):

--- FAIL: TestBatchedAssetIssuance (87.41s)
    --- FAIL: TestBatchedAssetIssuance/minting_with_cancellation (61.97s)
        test_sqlite.go:11: Creating new SQLite DB handle for testing: /tmp/TestBatchedAssetIssuanceminting_with_cancellation1885226529/001/tmp.db
        planter_test.go:313: 
                Error Trace:    /home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:313
                                            /home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:1313
                                            /home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:2051
                Error:          Condition never satisfied
                Test:           TestBatchedAssetIssuance/minting_with_cancellation

[gemini-code-assist]

Summary of Changes

Hello @ffranr, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses test flakiness in the tapgarden package, specifically within the queueSeedlingsInBatch test, by enhancing the stability and reliability of the MockKeyRing. The changes involve correcting mock return values, implementing more robust locking mechanisms, and introducing an atomic counter for key derivation calls. These improvements aim to eliminate race conditions and provide more accurate and consistent test assertions, ultimately leading to a more stable CI environment.

Highlights

• MockKeyRing Hardening: The MockKeyRing implementation has been made more robust by correctly initializing return values for mocked methods and switching from read-locks (RLock) to full mutex locks (Lock) in several methods to prevent potential race conditions.
• Atomic Counter for Key Derivation: An atomic counter (deriveNextKeyCallCount) was introduced in MockKeyRing to accurately track calls to DeriveNextKey, decoupling this count from the mock's internal call history and its mutex.
• Flaky Test Fix: The queueSeedlingsInBatch test in planter_test.go was refactored to use the new atomic counter for key derivation calls and wait.NoError instead of require.Eventually. The assertion now checks for >= expected calls, making the test more resilient to timing variations.
• Improved Test Helper: The test helper now explicitly resets the key derivation call count before each seedling processing, ensuring accurate tracking within the test loop.

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[gemini-code-assist]

Code Review

This pull request effectively addresses the flaky test TestBatchedAssetIssuance/minting_with_cancellation by hardening the MockKeyRing and refining the test logic. The introduction of an atomic counter for DeriveNextKey calls is a robust solution to avoid race conditions in test assertions. Replacing read locks with full mutex locks provides stronger consistency guarantees for the mock object. The test helper queueSeedlingsInBatch is also improved by using wait.NoError, which is more suitable for the asynchronous nature of the test.

My review includes a couple of suggestions to enhance the comments for the new exported functions in tapgarden/mock.go to better align with the project's documentation standards.

[jtobin]

LGTM. 👍

[GeorgeTsagk]

LGTM