test: add seqno recovery test for remove()

tests/seqno_recovery.rs

@@ -66,3 +66,47 @@ fn recover_seqno() -> fjall::Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn recover_seqno_tombstone() -> fjall::Result<()> {
+    let folder = tempfile::tempdir()?;
+
+    let mut seqno = 0;
+
+    // NOTE: clippy bug
+    #[allow(unused_assignments)]
+    {
+        let keyspace = Config::new(&folder).open()?;
+
+        let partitions = &[
+            keyspace.open_partition("default1", PartitionCreateOptions::default())?,
+            keyspace.open_partition("default2", PartitionCreateOptions::default())?,
+            keyspace.open_partition("default3", PartitionCreateOptions::default())?,
+        ];
+
+        for tree in partitions {
+            for x in 0..ITEM_COUNT as u64 {
+                let key = x.to_be_bytes();
+                tree.remove(key)?;
+
+                seqno += 1;
+                assert_eq!(seqno, keyspace.instant());
+            }
+
+            for x in 0..ITEM_COUNT as u64 {
+                let key: [u8; 8] = (x + ITEM_COUNT as u64).to_be_bytes();
+                tree.remove(key)?;
+
+                seqno += 1;
+                assert_eq!(seqno, keyspace.instant());
+            }
+        }
+    }
+
+    for _ in 0..10 {
+        let keyspace = Config::new(&folder).open()?;
+        assert_eq!(seqno, keyspace.instant());
+    }
+
+    Ok(())
+}