Add DepositableDelegateProxy tests

contracts/test/helpers/ProxyTarget.sol

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+pragma solidity 0.4.24;
+
+contract ProxyTarget {
+    event Pong();
+
+    function ping() external {
+      emit Pong();
+    }
+}
+
+contract ProxyTargetWithFallback is ProxyTarget {
+    event ReceivedEth();
+
+    function () external payable {
+      emit ReceivedEth();
+    }
+}

contracts/test/mocks/apps/DepositableDelegateProxyMock.sol

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+pragma solidity 0.4.24;
+
+import "../../../common/DepositableDelegateProxy.sol";
+
+
+contract DepositableDelegateProxyMock is DepositableDelegateProxy {
+    address private implementationMock;
+
+    function enableDepositsOnMock() external {
+        setDepositable(true);
+    }
+
+    function setImplementationOnMock(address _implementationMock) external {
+        implementationMock = _implementationMock;
+    }
+
+    function implementation() public view returns (address) {
+        return implementationMock;
+    }
+
+    function proxyType() public pure returns (uint256 proxyTypeId) {
+        return UPGRADEABLE;
+    }
+}

test/contracts/common/depositable_delegate_proxy.js

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+const { toChecksumAddress } = require('web3-utils')
+const { assertAmountOfEvents, assertEvent } = require('../../helpers/assertEvent')(web3)
+const { decodeEventsOfType } = require('../../helpers/decodeEvent')
+const { assertRevert, assertOutOfGas } = require('../../helpers/assertThrow')
+const { getBalance } = require('../../helpers/web3')
+
+// Mocks
+const DepositableDelegateProxyMock = artifacts.require('DepositableDelegateProxyMock')
+const EthSender = artifacts.require('EthSender')
+const ProxyTarget = artifacts.require('ProxyTarget')
+const ProxyTargetWithFallback = artifacts.require('ProxyTargetWithFallback')
+
+const TX_BASE_GAS = 21000
+const SEND_ETH_GAS = TX_BASE_GAS + 9999 // 10k gas is the threshold for depositing
+const FALLBACK_SETUP_GAS = 100 // rough estimation of how much gas it spends before executing the fallback code
+const SOLIDITY_TRANSFER_GAS = 2300
+const ISTANBUL_SLOAD_GAS_INCREASE = 600
+
+contract('DepositableDelegateProxy', ([ sender ]) => {
+  let ethSender, proxy, proxyTargetBase, proxyTargetWithFallbackBase
+
+  // Initial setup
+  before(async () => {
+    ethSender = await EthSender.new()
+    proxyTargetBase = await ProxyTarget.new()
+    proxyTargetWithFallbackBase = await ProxyTargetWithFallback.new()
+  })
+
+  beforeEach(async () => {
+    proxy = await DepositableDelegateProxyMock.new()
+  })
+
+  const itForwardsToImplementationIfGasIsOverThreshold = () => {
+    let target
+
+    beforeEach(() => {
+      target = ProxyTargetWithFallback.at(proxy.address)
+    })
+
+    context('when implementation address is set', () => {
+      const itSuccessfullyForwardsCall = () => {
+        it('forwards call with data', async () => {
+          const receipt = await target.ping()
+          assertAmountOfEvents(receipt, 'Pong')
+        })
+      }
+
+      context('when implementation has a fallback', () => {
+        beforeEach(async () => {
+          await proxy.setImplementationOnMock(proxyTargetWithFallbackBase.address)
+        })
+
+        itSuccessfullyForwardsCall()
+
+        it('can receive ETH', async () => {
+          const receipt = await target.sendTransaction({ value: 1, gas: SEND_ETH_GAS + FALLBACK_SETUP_GAS })
+          assertAmountOfEvents(receipt, 'ReceivedEth')
+        })
+      })
+
+      context('when implementation doesn\'t have a fallback', () => {
+        beforeEach(async () => {
+          await proxy.setImplementationOnMock(proxyTargetBase.address)
+        })
+
+        itSuccessfullyForwardsCall()
+
+        it('reverts when sending ETH', async () => {
+          await assertRevert(target.sendTransaction({ value: 1 }))
+        })
+      })
+    })
+
+    context('when implementation address is not set', () => {
+      it('reverts when a function is called', async () => {
+        await assertRevert(target.ping())
+      })
+
+      it('reverts when sending ETH', async () => {
+        await assertRevert(target.sendTransaction({ value: 1 }))
+      })
+    })
+  }
+
+  const itRevertsOnInvalidDeposits = () => {
+    it('reverts when call has data', async () => {
+      await assertRevert(proxy.sendTransaction({ value: 1, data: '0x01', gas: SEND_ETH_GAS }))
+    })
+
+    it('reverts when call sends 0 value', async () => {
+      await assertRevert(proxy.sendTransaction({ value: 0, gas: SEND_ETH_GAS }))
+    })
+  }
+
+  context('when proxy is set as depositable', () => {
+    beforeEach(async () => {
+      await proxy.enableDepositsOnMock()
+    })
+
+    context('when call gas is below the forwarding threshold', () => {
+      const value = 100
+
+      const sendEthToProxy = async ({ value, gas, shouldOOG }) => {
+        const initialBalance = await getBalance(proxy.address)
+
+        const sendEthAction = () => proxy.sendTransaction({ from: sender, gas, value })
+
+        if (shouldOOG) {
+          await assertOutOfGas(sendEthAction())
+          assert.equal((await getBalance(proxy.address)).valueOf(), initialBalance, 'Target balance should be the same as before')
+        } else {
+          const { receipt, logs } = await sendEthAction()
+
+          assert.equal((await getBalance(proxy.address)).valueOf(), initialBalance.plus(value), 'Target balance should be correct')
+          assertAmountOfEvents({ logs }, 'ProxyDeposit')
+          assertEvent({ logs }, 'ProxyDeposit', { sender, value })
+
+          return receipt
+        }
+      }
+
+      it('can receive ETH (Constantinople)', async () => {
+        const { gasUsed } = await sendEthToProxy({ value, gas: SEND_ETH_GAS })
+        console.log('Used gas:', gasUsed - TX_BASE_GAS)
+      })
+
+      // TODO: Remove when the targetted EVM has been upgraded to Istanbul (EIP-1884)
+      it('can receive ETH (Istanbul, EIP-1884)', async () => {
+        const gas = TX_BASE_GAS + SOLIDITY_TRANSFER_GAS - ISTANBUL_SLOAD_GAS_INCREASE
+        const { gasUsed } = await sendEthToProxy({ value, gas })
+        const gasUsedIstanbul = gasUsed - TX_BASE_GAS + ISTANBUL_SLOAD_GAS_INCREASE
+        console.log('Used gas (Istanbul):', gasUsedIstanbul)
+
+        assert.isBelow(gasUsedIstanbul, 2300, 'Gas cost under Istanbul cannot be above 2300 gas')
+      })
+
+      // TODO: Remove when the targetted EVM has been upgraded to Istanbul (EIP-1884)
+      it('cannot receive ETH if sent with a small amount of gas', async () => {
+        // deposit cannot be done with this amount of gas
+        const gas = TX_BASE_GAS + SOLIDITY_TRANSFER_GAS - ISTANBUL_SLOAD_GAS_INCREASE - 250
+        await sendEthToProxy({ shouldOOG: true, value, gas })
+      })
+
+      it('can receive ETH from contract', async () => {
+        const { tx } = await ethSender.sendEth(proxy.address, { value })
+        const receipt = await web3.eth.getTransactionReceipt(tx)
+        const logs = decodeEventsOfType(receipt, DepositableDelegateProxyMock.abi, 'ProxyDeposit')
+        assertAmountOfEvents({ logs }, 'ProxyDeposit')
+        assertEvent({ logs }, 'ProxyDeposit', { sender: toChecksumAddress(ethSender.address), value })
+      })
+
+      itRevertsOnInvalidDeposits()
+    })
+
+    context('when call gas is over forwarding threshold', () => {
+      itForwardsToImplementationIfGasIsOverThreshold()
+    })
+  })
+
+  context('when proxy is not set as depositable', () => {
+    context('when call gas is below the forwarding threshold', () => {
+      it('reverts when depositing ETH', async () => {
+        await assertRevert(proxy.sendTransaction({ value: 1, gas: SEND_ETH_GAS }))
+      })
+
+      itRevertsOnInvalidDeposits()
+    })
+
+    context('when call gas is over forwarding threshold', () => {
+      itForwardsToImplementationIfGasIsOverThreshold()
+    })
+  })
+})