implement self balance

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/contracts/Value.sol

@@ -7,6 +7,7 @@ pragma solidity ^0.8;
     "actions": [
         {
             "Instantiate": {
+                "value": 1024,
                 "code": {
                     "Solidity": {
                         "contract": "Value"
@@ -22,16 +23,30 @@ pragma solidity ^0.8;
                 "value": 123,
                 "data": "3fa4f245"
             }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "52da5fa0"
+            }
         }
     ]
 }
 */
 
 contract Value {
+    constructor() payable {}
+
     function value() public payable returns (uint ret) {
         ret = msg.value;
     }
 
+    function balance_self() public view returns (uint ret) {
+        ret = address(this).balance;
+    }
+
     function balance_of(address _address) public view returns (uint ret) {
         ret = _address.balance;
     }

crates/integration/src/cases.rs

@@ -209,9 +209,11 @@ case!("Call.sol", "Call", vec![], call_constructor);
 sol!(
     contract Value {
         function balance_of(address _address) public view returns (uint ret);
+        function balance_self() public view returns (uint ret);
     }
 );
 case!("Value.sol", Value, balance_ofCall, value_balance_of, address: Address);
+case!("Value.sol", Value, balance_selfCall, value_balance_self,);
 
 sol!(
     contract Bitwise {

crates/integration/src/tests.rs

@@ -26,7 +26,6 @@ test_spec!(hash_keccak_256, "TestSha3", "Crypto.sol");
 test_spec!(erc20, "ERC20", "ERC20.sol");
 test_spec!(computation, "Computation", "Computation.sol");
 test_spec!(msize, "MSize", "MSize.sol");
-test_spec!(transferred_value, "Value", "Value.sol");
 test_spec!(sha1, "SHA1", "SHA1.sol");
 test_spec!(block, "Block", "Block.sol");
 test_spec!(mcopy, "MCopy", "MCopy.sol");
@@ -34,6 +33,7 @@ test_spec!(events, "Events", "Events.sol");
 test_spec!(storage, "Storage", "Storage.sol");
 test_spec!(mstore8, "MStore8", "MStore8.sol");
 test_spec!(address, "Context", "Context.sol");
+test_spec!(balance, "Value", "Value.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {