test(FeeHandlerSeller.t.sol): adds MVP contract outline

Test is currently failing

packages/protocol/test-sol/unit/common/FeeHandlerSeller.t.sol

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.5.13;
+pragma experimental ABIEncoderV2;
+
+// Helper contracts
+import { Test } from "celo-foundry/Test.sol";
+import { TestConstants } from "@test-sol/constants.sol";
+
+// Contract to test
+import "@celo-contracts/common/FeeHandler.sol";
+
+// Dependencies
+import { GoldToken } from "@celo-contracts/common/GoldToken.sol";
+import { IFeeHandlerSeller } from "@celo-contracts/common/interfaces/IFeeHandlerSeller.sol";
+import { MentoFeeHandlerSeller } from "@celo-contracts/common/MentoFeeHandlerSeller.sol";
+import { UniswapFeeHandlerSeller } from "@celo-contracts/common/UniswapFeeHandlerSeller.sol";
+
+contract FeeHandlerSellerTest is Test, TestConstants {
+  // Constants
+  uint256 constant ONE_CELOTOKEN = 1000000000000000000;
+
+  // Actors
+  address receiver = actor("receiver");
+
+  // Contract instances
+  IRegistry registry;
+  GoldToken celoToken;
+  IFeeHandlerSeller mentoFeeHandlerSeller;
+  IFeeHandlerSeller uniswapFeeHandlerSeller;
+
+  // Helper data structures
+  IFeeHandlerSeller[] contractsToTest;
+
+  function setUp() public {
+    // owner = address(this);
+    // vm.prank(owner);
+
+    // Boilerplate
+    deployCodeTo("Registry.sol", abi.encode(false), REGISTRY_ADDRESS);
+    registry = IRegistry(REGISTRY_ADDRESS);
+    celoToken = new GoldToken(true);
+
+    // Contracts to be tested
+    mentoFeeHandlerSeller = new MentoFeeHandlerSeller(true);
+    uniswapFeeHandlerSeller = new UniswapFeeHandlerSeller(true);
+
+    contractsToTest.push(mentoFeeHandlerSeller);
+    contractsToTest.push(uniswapFeeHandlerSeller);
+
+    // registry.setAddressFor("GoldToken", address(celoToken));
+    // registry.setAddressFor("CeloToken", address(celoToken));
+  }
+}
+
+contract FeeHandlerSellerTest_Transfer is FeeHandlerSellerTest {
+  function test_ShouldTransfer() public {
+    /* 
+      for (const contract of contractsToTest) {
+        const receiver = web3.eth.accounts.create().address
+        assertEqualBN(await goldToken.balanceOf(receiver), new BigNumber(0))
+
+        await goldToken.transfer(contract.address, oneCelo)
+        await contract.transfer(goldToken.address, oneCelo, receiver)
+        assertEqualBN(await goldToken.balanceOf(receiver), oneCelo)
+        assertEqualBN(await goldToken.balanceOf(contract.address), new BigNumber(0))
+      }
+      */
+    for (uint256 i = 0; i < contractsToTest.length; i++) {
+      assertEq(celoToken.balanceOf(receiver), 0, "Balance of receiver should be 0 at start");
+      vm.deal(address(contractsToTest[i]), ONE_CELOTOKEN); // Faucet contract
+
+      vm.prank(address(this));
+      contractsToTest[i].transfer(address(celoToken), ONE_CELOTOKEN, receiver); // Transfer from contract
+      assertEq(celoToken.balanceOf(receiver), 0, "Balance of receiver should be 1 after transfer");
+      assertEq(celoToken.balanceOf(address(contractsToTest[i])), 0, "Balance of contract should be 0");
+    }
+
+
+  }
+}