test(chain): Test apply_update with a single CheckPoint<Header>

Author: ValuedMammal

crates/chain/src/local_chain.rs

@@ -734,3 +734,67 @@ where
         Ok((new_tip, changeset))
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    use alloc::vec::Vec;
+    use bitcoin::block::Header;
+    use bitcoin::consensus::encode::deserialize_hex;
+    use bitcoin::hashes::Hash;
+
+    // Test that `apply_update` can connect 1 header at a time
+    // and fails if the hashes don't line up.
+    #[test]
+    fn test_apply_update_single_header() {
+        let headers: Vec<Header> = [
+            "0100000000000000000000000000000000000000000000000000000000000000000000003ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4adae5494dffff7f2002000000",
+            "0000002006226e46111a0b59caaf126043eb5bbf28c34f3a5e332a1fc7b2b73cf188910f1c96cc459dbb0c7bbc722af14f913da868779290ad48ff87ee314ebb8ae08f384b166069ffff7f2001000000",
+            "0000002078ce518c7dcfd99ad5859c35bd2be15794c0e5dc8e60c1fea3b0461c45da181ca80f828504f88c645ea46cfcf93156269807e3bd409e1317271a1546d238e9b24c166069ffff7f2001000000",
+            "000000200dfd6c5af6ea3cb341a08db344f93743d94b630d122867faff855f6310e58864e6e0c859fda703d66d051b86f16f09b0cead182f3cbe13767cd91b6371ec252c4c166069ffff7f2000000000",
+        ]
+        .into_iter()
+        .map(|s| deserialize_hex::<Header>(s).expect("failed to deserialize header"))
+        .collect();
+
+        let header_0 = headers[0];
+        let header_1 = headers[1];
+        let header_2 = headers[2];
+        let header_3 = headers[3];
+
+        let (mut chain, _) = LocalChain::from_genesis(header_0);
+
+        // Apply 1 `CheckPoint<Header>` at a time
+        for (height, header) in (1..).zip([header_1, header_2, header_3]) {
+            let changeset = chain.apply_update(CheckPoint::new(height, header)).unwrap();
+            assert_eq!(
+                changeset,
+                ChangeSet {
+                    blocks: [(height, Some(headers[height as usize]))].into()
+                },
+            );
+        }
+        assert_eq!(chain.tip.iter().count(), 4);
+        for height in 0..4 {
+            assert!(chain
+                .get(height)
+                .is_some_and(|cp| cp.hash() == headers[height as usize].block_hash()))
+        }
+
+        // `apply_update` should error if the hashes don't line up
+        chain = LocalChain::from_blocks([(0, header_0), (1, header_1)].into()).unwrap();
+        let mut header_2_alt = header_2;
+        header_2_alt.prev_blockhash = BlockHash::all_zeros();
+        let res = chain.apply_update(CheckPoint::new(2, header_2_alt));
+        assert!(
+            matches!(
+                res,
+                Err(CannotConnectError {
+                    try_include_height: 1
+                })
+            ),
+            "`apply_update` failed to detect hash conflict"
+        );
+    }
+}