ETH Delegating

solidity/contracts/fully-backed/FullyBackedBonding.sol

@@ -41,6 +41,8 @@ contract FullyBackedBonding is
         uint256 value
     );
 
+    event OperatorToppedUp(address indexed operator, uint256 value);
+
     // The ether value (in wei) that should be passed along with the delegation
     // and deposited for bonding.
     uint256 public constant MINIMUM_DELEGATION_DEPOSIT = 40 ether;
@@ -104,6 +106,18 @@ contract FullyBackedBonding is
         emit OperatorDelegated(operator, beneficiary, authorizer, msg.value);
     }
 
+    /// @notice Top-ups operator's unbonded value.
+    /// @dev This function should be used to add new unbonded value to the system
+    /// for an operator. The `deposit` function defined in parent abstract contract
+    /// should be called only by applications returning value that has been already
+    /// initially deposited and seized later.
+    /// @param operator Address of the operator.
+    function topUp(address operator) public payable {
+        deposit(operator);
+
+        emit OperatorToppedUp(operator, msg.value);
+    }
+
     /// @notice Checks if the operator for the given bond creator contract
     /// has passed the initialization period.
     /// @param operator The operator address.

solidity/test/FullyBackedBondingTest.js

@@ -204,6 +204,54 @@ describe("FullyBackedBonding", function () {
     })
   })
 
+  describe("topUp", async () => {
+    const value = new BN(123)
+
+    let initialDeposit
+
+    before(async () => {
+      initialDeposit = minimumDelegationValue
+
+      await bonding.delegate(operator, beneficiary, authorizer, {
+        from: owner,
+        value: initialDeposit,
+      })
+    })
+
+    it("adds value to deposited on delegation", async () => {
+      const expectedFinalBalance = initialDeposit.add(value)
+
+      await bonding.topUp(operator, {
+        value: value,
+      })
+
+      expect(await bonding.unbondedValue(operator)).to.eq.BN(
+        expectedFinalBalance,
+        "invalid final unbonded value"
+      )
+    })
+
+    it("emits event", async () => {
+      const receipt = await bonding.topUp(operator, {
+        value: value,
+      })
+
+      expectEvent(receipt, "OperatorToppedUp", {
+        operator: operator,
+        value: value,
+      })
+    })
+
+    it("reverts when no delegation happened", async () => {
+      await expectRevert(
+        bonding.topUp(thirdParty, {
+          value: new BN(123),
+        }),
+        "Beneficiary not defined for the operator"
+      )
+    })
+  })
+
   describe("deposit", async () => {
     it("adds value to deposited on delegation", async () => {
       const initialDeposit = minimumDelegationValue