test: check that `listdescriptors` descriptor strings are sorted #26156

This small PR adds a test for the change introduced in PR #25931 ("rpc: sort listdescriptors result", commit 50996241f2b0eefeaab4fcd11b9730fa2dc107ae). The correctness of the test can easily be verified by commenting out the std::sort call in the listdescriptors RPC implementation:

diff --git a/src/wallet/rpc/backup.cpp b/src/wallet/rpc/backup.cpp
index 09c74ea2da..3ed1a69b26 100644
--- a/src/wallet/rpc/backup.cpp
+++ b/src/wallet/rpc/backup.cpp
@@ -1829,9 +1829,11 @@ RPCHelpMan listdescriptors()
         });
     }

+    /*
     std::sort(wallet_descriptors.begin(), wallet_descriptors.end(), [](const auto& a, const auto& b) {
         return a.descriptor < b.descriptor;
     });
+    */

     UniValue descriptors(UniValue::VARR);
     for (const WalletDescInfo& info : wallet_descriptors) {

leading to a fail of the functional test wallet_listdescriptors.py.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #25747 (rpc: add ability to export/import descriptor files in listdescriptors and importdescriptors by w0xlt)

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.

Should the help for this rpc and the entry for this rpc in descriptors.md be updated to mention that it is sorted?

Should the help for this rpc and the entry for this rpc in descriptors.md be updated to mention that it is sorted?

Good point. I think for descriptors.md this is too much of a detail to be mentioned (the file only gives a rough one-line description of what each RPC does), but for the RPC help it would make sense. Will take a look.

Added a commit that extends the listdescriptors RPC help (https://github.com/bitcoin/bitcoin/pull/26156/commits/810c3dc7efbfa07e81f161848010e886e04929ea) by mentioning that the result is sorted by descriptor string representation, as suggested by @jarolrod.

ACK 810c3dc7efbfa07e81f161848010e886e04929ea

ACK 810c3dc7efbfa07e81f161848010e886e04929ea