fix: wrong subtract timestamp (#6097)

crates/anvil/src/eth/backend/mem/mod.rs

@@ -659,9 +659,7 @@ impl Backend {
             let block =
                 self.block_by_hash(best_block_hash).await?.ok_or(BlockchainError::BlockNotFound)?;
 
-            // Note: In [`TimeManager::compute_next_timestamp`] we ensure that the next timestamp is
-            // always increasing by at least one. By subtracting 1 here, this is mitigated.
-            let reset_time = block.timestamp.as_u64().saturating_sub(1);
+            let reset_time = block.timestamp.as_u64();
             self.time.reset(reset_time);
             self.set_block_number(num.into());
         }

crates/anvil/tests/it/anvil_api.rs

@@ -498,3 +498,23 @@ async fn test_set_chain_id() {
     let chain_id = provider.get_chainid().await.unwrap();
     assert_eq!(chain_id, U256::from(1234));
 }
+
+// <https://github.com/foundry-rs/foundry/issues/6096>
+#[tokio::test(flavor = "multi_thread")]
+async fn test_fork_revert_next_block_timestamp() {
+    let (api, _handle) = spawn(fork_config()).await;
+
+    // Mine a new block, and check the new block gas limit
+    api.mine_one().await;
+    let latest_block = api.block_by_number(BlockNumber::Latest).await.unwrap().unwrap();
+
+    let snapshot_id = api.evm_snapshot().await.unwrap();
+    api.mine_one().await;
+    api.evm_revert(snapshot_id).await.unwrap();
+    let block = api.block_by_number(BlockNumber::Latest).await.unwrap().unwrap();
+    assert_eq!(block, latest_block);
+
+    api.mine_one().await;
+    let block = api.block_by_number(BlockNumber::Latest).await.unwrap().unwrap();
+    assert!(block.timestamp > latest_block.timestamp);
+}