[Ethereum] Mock Smart Contract For Unit Testing

contract-designsoliditystoragetruffleunittesting

I'm new to Ethereum and solidity, I'm developing a simple decentralized application using Truffle where I have an abstract contract Storage and another contract Reader which uses storage.

contract Storage {
    function getWeight() public view returns(uint8);
    function setWeight(uint8 weight) public view returns(bool); 
}

contract Reader {
    Storage private storage;
    constructor(address storageAddress) {
        storage = Storage(storageAddress);
    }
}

I'm trying to write unit test for contract Reader, is there anyway to mock the behavior of the abstract contract? If not, then what is the best practices for that situation?

Best Answer

I created a little implementation of the Storage contract. Note that I renamed your abstraction to StorageInterface.

I also added some functions to Reader, since there isn't much to test unless it does something. So, now you have a setter/getter in the Reader that forwards to a Storage contract which is an implementation of the interface.

On looking at it, I decided I was uncomfortable with using "Storage" because this is a reserved word in the lower case form. I also dispensed with the uint8 that looks like premature optimization.

One other little thing. The Interface declared the setter as view, but it can't be since it writes to the contract state.

pragma solidity 0.4.24;

contract StoreInterface {
    function getWeight() public view returns(uint);
    function setWeight(uint weight) public returns(bool); 
}

/**
 * Just a very simple set of stubs ...
 * Deploy a "Store" and then pass its address into Reader's constructor.
 */

contract Store is StoreInterface {

    uint weight;

    event LogSetWeight(address sender, uint weight);

    function getWeight() public view returns(uint) {
        return weight;
    }

    function setWeight(uint _weight) public returns(bool) {
        weight = _weight;
        emit LogSetWeight(msg.sender, _weight);
        return true;
    } 
}

contract Reader {

    StoreInterface store;

    constructor(address storeAddress) public {
        store = StoreInterface(storeAddress);
    }

    function getWeight() public view returns(uint) {
        return store.getWeight();
    }

    function setWeight(uint weight) public returns(bool) {
        return store.setWeight(weight);
    }
}

Hope it helps.

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[Ethereum] Smart Contract Error: Returned values aren’t valid, did it run Out of Gas

I fixed the similar error by deleting .json files from build/contracts folder and then running truffle migrate in the terminal.

However, the error occurred in Visual Studio Code, not Remix IDE. It appeared after running truffle migrate --reset.

I'd like to add to this comment, after you delete .json files from build/contracts folder the problem persisted until I deleted files from the trash🗑 😅 So make sure trash is empty

How can i resolve this Remix compilation error “TypeError: Invalid array length, expected integer literal or constant expression & Data location “

I changed your smart contract implementation with this smart contract.

I put notes just so you'd know your errors.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

// NOTE: Import IERC20 contract
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

// NOTE: You must to implement IERC20 for override ERC20 methods!
contract NewToken is IERC20 {

  string public constant name = "NewToken";
  string public constant symbol = "NTKN";
  uint8 public constant decimals = 18;
  uint256 totalSupply_ = 10000000000000000000000000; 

  mapping(address => uint256) public balances;
  mapping(address => mapping (address => uint256)) allowed;

  // NOTE: I removed the events because it already defined into IERC20
  
  constructor() { 
    balances[msg.sender] = totalSupply_;
  }

  function totalSupply() public override view returns (uint256) {
    return totalSupply_;
  }

  // NOTE: You must to change signature function adding address parameter
  function balanceOf(address _address) public override view returns(uint256) {
    return balances[_address];
  }

  function transfer(address to, uint256 value) public override returns (bool) {
      require(value <= balances[msg.sender]);
      balances[msg.sender] = balances[msg.sender]-value;
      balances[to] = balances[to]+value;
      // NOTE: The event is called  Transfer not 'transfer'
      emit Transfer(msg.sender, to, value);
      return true;
  }

  function approve(address spender, uint256 value) public override returns (bool) {
      allowed[msg.sender][spender] = value;
      emit Approval(msg.sender, spender, value);
      return true;
  }

  function allowance(address owner, address spender) public override view returns (uint) {
      return allowed[owner][spender];
  }

  function transferFrom(address from, address to, uint256 value) public override returns (bool) {
      require(value <= balances[from]);
      require(value <= allowed[from][msg.sender]);

      balances[from] = balances[from]-value;
      allowed[from][msg.sender] = allowed[from][msg.sender]+value;
      balances[to] = balances[to]+value;
      emit Transfer(from, to, value);
      return true;
  }
}

Best Answer

Related Solutions

[Ethereum] Smart Contract Error: Returned values aren’t valid, did it run Out of Gas

How can i resolve this Remix compilation error “TypeError: Invalid array length, expected integer literal or constant expression & Data location “

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