fix: Blockhash of current block should be zero

crates/zksync/core/src/vm/runner.rs

@@ -277,7 +277,7 @@ pub fn encode_create_params(
 /// Get last 256 block hashes mapped to block numbers
 fn get_historical_block_hashes<DB: Database>(ecx: &mut EvmContext<DB>) -> HashMap<rU256, B256> {
     let mut block_hashes = HashMap::default();
-    for i in 0..256u32 {
+    for i in 1..=256u32 {
         let (block_number, overflow) = ecx.env.block.number.overflowing_sub(rU256::from(i));
         if overflow {
             break

crates/zksync/core/src/vm/tracer.rs

@@ -310,8 +310,10 @@ impl<S: Send, H: HistoryMode> DynTracer<S, SimpleMemory<H>> for CheatcodeTracer
                     self.call_context.block_hashes.get(&block_number.to_ru256())
                 {
                     self.farcall_handler.set_immediate_return(block_hash.to_vec());
-                    return;
+                } else {
+                    self.farcall_handler.set_immediate_return(rU256::ZERO.to_be_bytes_vec());
                 }
+                return;
             }
         }
 

zk-tests/src/Basic.t.sol

@@ -96,13 +96,20 @@ contract ZkBasicTest is Test {
             be.chainid() == block.chainid,
             "propagated block chainid is the same as current"
         );
+
         require(
             be.ZkBlockhash(block.number) == blockhash(block.number),
-            "propagated blockhash is the same as current"
+            "Blockhash of the current block should be zero"
         );
+
         require(
-            be.ZkBlockhash(block.number) == bytes32(0),
-            "blockhash mismatch"
+            be.ZkBlockhash(block.number - 1) == blockhash(block.number - 1),
+            "Blockhash of the previous block should be equal"
+        );
+
+        require(
+            be.ZkBlockhash(0) == blockhash(0),
+            "Blockhash of the genesis block should be equal"
         );
 
         be = new BlockEnv();