add test to read EVM contract from ReadBuf

chain-impl-mockchain/src/smartcontract/mod.rs

@@ -55,3 +55,56 @@ impl Payload for Contract {
         todo!();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use typed_bytes::ByteBuilder;
+
+    #[cfg(feature = "evm")]
+    #[test]
+    fn test_readable_evm_contract() {
+        use chain_core::mempack::ReadBuf;
+        use typed_bytes::ByteArray;
+
+        let from = AccountAddress::random();
+        let to = None;
+        let gas: Gas = 10000.into();
+        let gas_price: GasPrice = 2000.into();
+        let value = None;
+        let data = None;
+
+        let contract_type = 0; // Contract::EVM = 0
+        let has_to = 0;
+        let has_gas = 1;
+        let has_gas_price = 1;
+        let has_value = 0;
+        let has_data = 0;
+
+        let bb: ByteArray<Contract> = ByteBuilder::new()
+            .u8(contract_type)
+            .bytes(from.as_fixed_bytes())
+            .u8(has_to)
+            .u8(has_gas)
+            .bytes(&<[u8; 32]>::from(gas))
+            .u8(has_gas_price)
+            .bytes(&<[u8; 32]>::from(gas_price))
+            .u8(has_value)
+            .u8(has_data)
+            .finalize();
+
+        let mut readbuf = ReadBuf::from(bb.as_slice());
+        let contract = Contract::read(&mut readbuf).unwrap();
+
+        let expected = Contract::EVM {
+            from,
+            to,
+            gas: Some(gas),
+            gas_price: Some(gas_price),
+            value,
+            data,
+        };
+
+        assert_eq!(contract, expected);
+    }
+}