Removed balance variable from ETHApp.sol (paritytech#567)

* Removed non-required balance variable

* Added reject message

* removed require condition

ethereum/contracts/ETHApp.sol

@@ -16,8 +16,6 @@ contract ETHApp is RewardSource, AccessControl {
     using ScaleCodec for uint256;
     using ScaleCodec for uint32;
 
-    uint256 public balance;
-
     mapping(ChannelId => Channel) public channels;
 
     event Locked(
@@ -46,7 +44,6 @@ contract ETHApp is RewardSource, AccessControl {
         Channel memory _basic,
         Channel memory _incentivized
     ) {
-        balance = 0;
 
         Channel storage c1 = channels[ChannelId.Basic];
         c1.inbound = _basic.inbound;
@@ -73,8 +70,6 @@ contract ETHApp is RewardSource, AccessControl {
             "Invalid channel ID"
         );
 
-        balance = balance + msg.value;
-
         emit Locked(msg.sender, _recipient, msg.value, _paraId);
 
         bytes memory call;
@@ -105,12 +100,7 @@ contract ETHApp is RewardSource, AccessControl {
         uint256 _amount
     ) public onlyRole(INBOUND_CHANNEL_ROLE) {
         require(_amount > 0, "Must unlock a positive amount");
-        require(
-            balance >= _amount,
-            "ETH token balances insufficient to fulfill the unlock request"
-        );
 
-        balance = balance - _amount;
         (bool success, ) = _recipient.call{value: _amount}("");
         require(success, "Unable to send Ether");
         emit Unlocked(_sender, _recipient, _amount);

ethereum/test/test_eth_app.js

@@ -54,7 +54,8 @@ describe("ETHApp", function () {
     });
 
     it("should lock funds", async function () {
-      const beforeBalance = BigNumber(await this.app.balance());
+
+      const beforeBalance = BigNumber(await web3.eth.getBalance(this.app.address));
       const amount = BigNumber(web3.utils.toWei("0.25", "ether"));
 
       const tx = await lockupFunds(this.app, userOne, POLKADOT_ADDRESS, amount, ChannelId.Basic)
@@ -71,11 +72,8 @@ describe("ETHApp", function () {
 
       // Confirm contract's balance has increased
       const afterBalance = await web3.eth.getBalance(this.app.address);
-      afterBalance.should.be.bignumber.equal(amount);
+      afterBalance.should.be.bignumber.equal(beforeBalance.plus(amount));
 
-      // Confirm contract's locked balance state has increased by amount locked
-      const afterBalanceState = BigNumber(await this.app.balance());
-      afterBalanceState.should.be.bignumber.equal(beforeBalance.plus(amount));
     });
   })
 
@@ -98,9 +96,20 @@ describe("ETHApp", function () {
       // expected amount to unlock
       const amount = web3.utils.toWei("1", "ether");
 
-      const beforeBalance = BigNumber(await this.app.balance());
+      const beforeBalance = BigNumber(await web3.eth.getBalance(this.app.address));
       const beforeRecipientBalance = BigNumber(await web3.eth.getBalance(recipient));
 
+      const unlockAmount = web3.utils.toBN( web3.utils.toWei("2", "ether")).add(web3.utils.toBN(1))
+
+       await this.app.unlock(
+        addressBytes(POLKADOT_ADDRESS),
+        recipient,
+        unlockAmount.toString(),
+        {
+          from: inboundChannel,
+        }
+      ).should.be.rejectedWith(/Unable to send Ether/);
+
       let { receipt } = await this.app.unlock(
         addressBytes(POLKADOT_ADDRESS),
         recipient,
@@ -121,7 +130,7 @@ describe("ETHApp", function () {
       event.recipient.should.be.equal(recipient);
       event.amount.eq(ethers.BigNumber.from(amount)).should.be.true;
 
-      const afterBalance = BigNumber(await this.app.balance());
+      const afterBalance = BigNumber(await web3.eth.getBalance(this.app.address));
       const afterRecipientBalance = BigNumber(await web3.eth.getBalance(recipient));
 
       afterBalance.should.be.bignumber.equal(beforeBalance.minus(amount));