Merge pull request #391 from rudygodoy/pr-224-tests

Added tests for PR #224

contracts/token/StandardToken.sol

@@ -63,5 +63,30 @@ contract StandardToken is ERC20, BasicToken {
   function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
     return allowed[_owner][_spender];
   }
+
+    /*
+   * approve should be called when allowed[_spender] == 0. To increment
+   * allowed value is better to use this function to avoid 2 calls (and wait until 
+   * the first transaction is mined)
+   * From MonolithDAO Token.sol
+   */
+  function increaseApproval (address _spender, uint _addedValue) 
+    returns (bool success) {
+    allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
+    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
+    return true;
+  }
+
+  function decreaseApproval (address _spender, uint _subtractedValue) 
+    returns (bool success) {
+    uint oldValue = allowed[msg.sender][_spender];
+    if (_subtractedValue > oldValue) {
+      allowed[msg.sender][_spender] = 0;
+    } else {
+      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
+    }
+    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
+    return true;
+  }
 
 }

test/StandardToken.js

@@ -70,4 +70,22 @@ contract('StandardToken', function(accounts) {
     }
   });
 
+  describe('validating allowance updates to spender', function() {
+    let preApproved;
+
+    it('should start with zero', async function() {
+      preApproved = await token.allowance(accounts[0], accounts[1]);
+      assert.equal(preApproved, 0);
+    })
+
+    it('should increase by 50 then decrease by 10', async function() {
+      await token.increaseApproval(accounts[1], 50);
+      let postIncrease = await token.allowance(accounts[0], accounts[1]);
+      preApproved.plus(50).should.be.bignumber.equal(postIncrease);
+      await token.decreaseApproval(accounts[1], 10);
+      let postDecrease = await token.allowance(accounts[0], accounts[1]);
+      postIncrease.minus(10).should.be.bignumber.equal(postDecrease);
+    })
+  });
+
 });