Ensure a non-zero fee in the Router OutInstruction gas fuzz test

processor/ethereum/erc20/src/tests.rs

@@ -11,3 +11,5 @@ fn selector_collisions() {
     crate::abi::SeraiIERC20::transferFromWithInInstruction00081948E0Call::SELECTOR
   );
 }
+
+// This is primarily tested via serai-processor-ethereum-router

processor/ethereum/router/contracts/Router.sol

@@ -441,6 +441,8 @@ contract Router is IRouterWithoutCollisions {
     unchecked {
       // The amount of bytes needed to represent the nonce
       uint256 bitsNeeded = 0;
+      // This only iterates up to 64-bits as this will never exceed 2**64 as a matter of
+      // practicality
       for (uint256 bits = 0; bits <= 64; bits += 8) {
         bool valueFits = nonce < (uint256(1) << bits);
         bool notPriorSet = bitsNeeded == 0;

processor/ethereum/router/src/gas.rs

@@ -225,6 +225,8 @@ impl Router {
   }
 
   /// The worst-case gas cost for a legacy transaction which executes this batch.
+  ///
+  /// This assumes the fee will be non-zero.
   pub fn execute_gas(&self, coin: Coin, fee_per_gas: U256, outs: &OutInstructions) -> u64 {
     // Unfortunately, we can't cache this in self, despite the following code being written such
     // that a common EVM instance could be used, as revm's types aren't Send/Sync and we expect the

processor/ethereum/router/src/tests/mod.rs

@@ -836,6 +836,7 @@ async fn fuzz_test_out_instructions_gas() {
         out_instructions.push((SeraiEthereumAddress::Address(address), amount_out));
       }
     }
+    let out_instructions_original = out_instructions.clone();
     let out_instructions = OutInstructions::from(out_instructions.as_slice());
 
     // Randomly decide the coin
@@ -852,13 +853,17 @@ async fn fuzz_test_out_instructions_gas() {
       Coin::Erc20(erc20.address())
     };
 
-    let fee_per_gas = U256::from(OsRng.next_u64() % 10);
+    let fee_per_gas = U256::from(1) + U256::from(OsRng.next_u64() % 10);
     let gas = test.router.execute_gas(coin, fee_per_gas, &out_instructions);
     let fee = U256::from(gas) * fee_per_gas;
     // All of these should have succeeded
     let (tx, gas_used) =
       test.execute(coin, fee, out_instructions.clone(), vec![true; out_instructions.0.len()]).await;
     let unused_gas = test.gas_unused_by_calls(&tx).await;
-    assert_eq!(gas_used + unused_gas, gas);
+    assert_eq!(
+      gas_used + unused_gas,
+      gas,
+      "{coin:?} {fee_per_gas:?} {out_instructions_original:?}"
+    );
   }
 }