Merge #763: Fix Wallet::descriptor_checksum to actually return the checksum

af0b369 Fix `Wallet::descriptor_checksum` to actually return the checksum (志宇)

Pull request description:

  ### Description

  `Wallet::descriptor_checksum` should return the checksum, not the descriptor without the checksum.

  ### Notes to the reviewers

  Please merge.

  ### Changelog notice

  Fix `Wallet::descriptor_checksum` to actually return the descriptor checksum.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### Bugfixes:

  ~* [ ] This pull request breaks the existing API~
  * [x] I've added tests to reproduce the issue which are now passing
  ~* [ ] I'm linking the issue being fixed by this PR~

ACKs for top commit:
  danielabrozzoni:
    ACK af0b369 - I run the test you added with the old code, and verified that the bug was there. I then run the test (with a few more dbg!() expressions) and manually verified that the problem is fixed.
  notmandatory:
    ACK af0b369

Tree-SHA512: 64a5b1f4708db6f6dcff2f6ef5e0a4c7d206e764d7602ea803c8cc002410326eb59eee770d9c91694dfbf07193ee3ff6bfe163bcbb3506cd7b2a6b59814a3e5c

Author: danielabrozzoni

src/wallet/mod.rs

@@ -1842,7 +1842,7 @@ where
             .to_string()
             .split_once('#')
             .unwrap()
-            .0
+            .1
             .to_string()
     }
 }
@@ -1938,6 +1938,22 @@ pub(crate) mod test {
     // OP_PUSH.
     const P2WPKH_FAKE_WITNESS_SIZE: usize = 106;
 
+    #[test]
+    fn test_descriptor_checksum() {
+        let (wallet, _, _) = get_funded_wallet(get_test_wpkh());
+        let checksum = wallet.descriptor_checksum(KeychainKind::External);
+        assert_eq!(checksum.len(), 8);
+
+        let raw_descriptor = wallet
+            .descriptor
+            .to_string()
+            .split_once('#')
+            .unwrap()
+            .0
+            .to_string();
+        assert_eq!(get_checksum(&raw_descriptor).unwrap(), checksum);
+    }
+
     #[test]
     fn test_get_funded_wallet_balance() {
         let (wallet, _, _) = get_funded_wallet(get_test_wpkh());