[WIP] Fix naive refund (#95)

* fix amountToRefund computation bug

* Add new test to ensure refund works. Update old test to be more strict on refund.

* Move test back into main file.

contract/contracts/CrowdFund.sol

@@ -38,6 +38,7 @@ contract CrowdFund {
     uint public deadline;
     uint public raiseGoal;
     uint public amountRaised;
+    uint public frozenBalance;
     uint public minimumContributionAmount;
     uint public amountVotingForRefund;
     address public beneficiary;
@@ -213,6 +214,7 @@ contract CrowdFund {
             freezeReason = FreezeReason.MAJORITY_VOTING_TO_REFUND;
         }
         frozen = true;
+        frozenBalance = address(this).balance;
     }
 
     // anyone can refund a contributor if a crowdfund has been frozen
@@ -222,8 +224,7 @@ contract CrowdFund {
         require(!isRefunded, "Specified address is already refunded");
         contributors[refundAddress].refunded = true;
         uint contributionAmount = contributors[refundAddress].contributionAmount;
-        // TODO - maybe don't use address(this).balance
-        uint amountToRefund = contributionAmount.mul(address(this).balance).div(raiseGoal);
+        uint amountToRefund = contributionAmount.mul(address(this).balance).div(frozenBalance);
         refundAddress.transfer(amountToRefund);
         emit Withdrawn(refundAddress, amountToRefund);
     }

contract/test/CrowdFundDeadlineTest.js

@@ -47,7 +47,11 @@ contract("CrowdFund Deadline", accounts => {
 
   it("allows anyone to refund after time is up and goal is not reached and sets refund reason to 1", async () => {
     const fundAmount = raiseGoal / 10;
-    await crowdFund.contribute({ from: fourthAccount, value: fundAmount });
+    await crowdFund.contribute({
+      from: fourthAccount,
+      value: fundAmount,
+      gasPrice: 0,
+    });
     assert.equal(
       (await crowdFund.contributors(fourthAccount))[0].toNumber(),
       fundAmount
@@ -59,7 +63,7 @@ contract("CrowdFund Deadline", accounts => {
     assert.equal((await crowdFund.getFreezeReason()), 1)
     await crowdFund.withdraw(fourthAccount);
     const finalBalance = await web3.eth.getBalance(fourthAccount);
-    assert.ok(finalBalance.greaterThan(initBalance)); // hard to be exact due to the gas usage
+    assert.ok(finalBalance.equals(initBalance.plus(fundAmount)));
   });
 
   it("refunds remaining proportionally when fundraiser has failed", async () => {

contract/test/CrowdFundTest.js

@@ -412,6 +412,24 @@ contract("CrowdFund", accounts => {
     assert.ok(finalBalanceThirdAccount.gt(initBalanceThirdAccount));
   });
 
+  it("refunds full amounts even if raise goal isn't reached", async () => {
+    const initialBalance = await web3.eth.getBalance(fourthAccount);
+    const contribution = raiseGoal / 2;
+    const receipt = await crowdFund.contribute({
+      from: fourthAccount,
+      value: contribution,
+      gasPrice: 0,
+    });
+    await crowdFund.refund({ from: firstTrusteeAccount });
+    await crowdFund.withdraw(fourthAccount);
+    const balance = await web3.eth.getBalance(fourthAccount);
+    const diff = initialBalance.minus(balance);
+    assert(
+      balance.equals(initialBalance),
+      `Expected full refund, but refund was short ${diff.toString()} wei`
+    );
+  });
+
   // [END] refund
   // [BEGIN] getContributorMilestoneVote