fntest: tweaked rpc_recent_blocks to maybe make it flake less

functional-tests/tests/rpc_recent_blocks.py

@@ -5,7 +5,8 @@
 from envs import testenv
 
 NUM_BLOCKS_TO_RECEIVE = 10
-BLOCK_NUMBER = 4
+CHECK_BLOCK_NUMBER = 6
+TRY_LIMIT = 20
 
 
 @flexitest.register
@@ -19,25 +20,27 @@ def main(self, ctx: flexitest.RunContext):
         # create both btc and sequencer RPC
         seqrpc = seq.create_rpc()
         counter = 0
-        while counter <= 20:
+        while counter < TRY_LIMIT:
             blk = seqrpc.strata_getHeadersAtIdx(NUM_BLOCKS_TO_RECEIVE)
-            if blk is None:
-                counter += 1
-                time.sleep(1)
-            else:
+            if blk is not None:
                 break
 
+            counter += 1
+            time.sleep(1)
+
+        assert counter < TRY_LIMIT, "seem to be not making progress"
+
         recent_blks = seqrpc.strata_getRecentBlockHeaders(NUM_BLOCKS_TO_RECEIVE)
-        assert len(recent_blks) == NUM_BLOCKS_TO_RECEIVE
+        assert len(recent_blks) == NUM_BLOCKS_TO_RECEIVE, f"got {len(recent_blks)} blocks back, asked for {NUM_BLOCKS_TO_RECEIVE}"
 
         # check if they are in order by verifying if N-1 block is parent of N block
         for idx in reversed(range(0, NUM_BLOCKS_TO_RECEIVE)):
             if idx != NUM_BLOCKS_TO_RECEIVE - 1:
                 assert recent_blks[idx]["prev_block"] == recent_blks[idx + 1]["block_id"]
 
-        l2_blk = seqrpc.strata_getHeadersAtIdx(recent_blks[BLOCK_NUMBER]["block_idx"])
+        l2_blk = seqrpc.strata_getHeadersAtIdx(recent_blks[CHECK_BLOCK_NUMBER]["block_idx"])
 
-        assert recent_blks[BLOCK_NUMBER]["block_idx"] == l2_blk[0]["block_idx"]
+        assert recent_blks[CHECK_BLOCK_NUMBER]["block_idx"] == l2_blk[0]["block_idx"]
 
         second_blk_from_id = seqrpc.strata_getHeaderById(l2_blk[0]["block_id"])