add IERC20Detailed contract and update TestToken constructor

contracts/ERC20Token.sol

@@ -1,15 +0,0 @@
-pragma solidity ^0.6.1;
-
-// https://github.com/ethereum/EIPs/issues/20
-
-interface ERC20Token {
-    event Transfer(address indexed _from, address indexed _to, uint256 _value);
-    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
-
-    function transfer(address _to, uint256 _value) external returns (bool success);
-    function approve(address _spender, uint256 _value) external returns (bool success);
-    function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);
-    function balanceOf(address _owner) external view returns (uint256 balance);
-    function allowance(address _owner, address _spender) external view returns (uint256 remaining);
-    function totalSupply() external view returns (uint256 supply);
-}

contracts/GiftBucket.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.6.1;
 pragma experimental ABIEncoderV2;
 
-import "./ERC20Token.sol";
+import "./IERC20.sol";
 
 contract GiftBucket {
 
@@ -9,7 +9,7 @@ contract GiftBucket {
 
   address payable public owner;
 
-  ERC20Token public tokenContract;
+  IERC20 public tokenContract;
 
   uint256 public expirationTime;
 
@@ -46,7 +46,7 @@ contract GiftBucket {
 
     require(_expirationTime > block.timestamp, "expiration can't be in the past");
 
-    tokenContract = ERC20Token(_tokenAddress);
+    tokenContract = IERC20(_tokenAddress);
     expirationTime = _expirationTime;
     owner = payable(_owner);
 

contracts/IERC20.sol

@@ -0,0 +1,15 @@
+pragma solidity ^0.6.1;
+
+// https://github.com/ethereum/EIPs/issues/20
+
+interface IERC20 {
+  event Transfer(address indexed _from, address indexed _to, uint256 _value);
+  event Approval(address indexed _owner, address indexed _spender, uint256 _value);
+
+  function transfer(address _to, uint256 _value) external returns (bool success);
+  function approve(address _spender, uint256 _value) external returns (bool success);
+  function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);
+  function balanceOf(address _owner) external view returns (uint256 balance);
+  function allowance(address _owner, address _spender) external view returns (uint256 remaining);
+  function totalSupply() external view returns (uint256 supply);
+}

contracts/IERC20Detailed.sol

@@ -0,0 +1,9 @@
+pragma solidity >=0.5.0 <0.7.0;
+
+import "./IERC20.sol";
+
+abstract contract IERC20Detailed is IERC20 {
+  function symbol() virtual public view returns (string memory);
+  function decimals() virtual public view returns (uint8);
+}
+

contracts/StandardToken.sol

@@ -1,8 +1,8 @@
 pragma solidity ^0.6.1;
 
-import "./ERC20Token.sol";
+import "./IERC20.sol";
 
-contract StandardToken is ERC20Token {
+contract StandardToken is IERC20 {
 
     uint256 private supply;
     mapping (address => uint256) balances;
@@ -15,7 +15,7 @@ contract StandardToken is ERC20Token {
         uint256 _value
     )
         external
-        override(ERC20Token)
+        override(IERC20)
         returns (bool success)
     {
         return transfer(msg.sender, _to, _value);
@@ -23,7 +23,7 @@ contract StandardToken is ERC20Token {
 
     function approve(address _spender, uint256 _value)
         external
-        override(ERC20Token)
+        override(IERC20)
         returns (bool success)
     {
         allowed[msg.sender][_spender] = _value;
@@ -37,7 +37,7 @@ contract StandardToken is ERC20Token {
         uint256 _value
     )
         external
-        override(ERC20Token)
+        override(IERC20)
         returns (bool success)
     {
         if (balances[_from] >= _value &&
@@ -53,7 +53,7 @@ contract StandardToken is ERC20Token {
     function allowance(address _owner, address _spender)
         external
         view
-        override(ERC20Token)
+        override(IERC20)
         returns (uint256 remaining)
     {
         return allowed[_owner][_spender];
@@ -62,7 +62,7 @@ contract StandardToken is ERC20Token {
     function balanceOf(address _owner)
         external
         view
-        override(ERC20Token)
+        override(IERC20)
         returns (uint256 balance)
     {
         return balances[_owner];
@@ -71,7 +71,7 @@ contract StandardToken is ERC20Token {
     function totalSupply()
         external
         view
-        override(ERC20Token)
+        override(IERC20)
         returns(uint256 currentTotalSupply)
     {
         return supply;

contracts/TestToken.sol

@@ -6,18 +6,32 @@ import "./StandardToken.sol";
  * @notice ERC20Token for test scripts, can be minted by anyone.
  */
 contract TestToken is StandardToken {
+  string private _symbol;
+  uint256 private _decimals;
 
-    constructor() public { }
+  constructor(string memory symbol, uint256 decimals) public {
+    _symbol = symbol;
+    _decimals = decimals;
+  }
 
-    fallback() external {
-      mint(1000);
-    }
+  fallback() external {
+    uint256 amount = 5000;
+    mint(amount * uint256(10)**_decimals);
+  }
 
-    /**
-     * @notice any caller can mint any `_amount`
-     * @param _amount how much to be minted
-     */
-    function mint(uint256 _amount) public {
-        mint(msg.sender, _amount);
-    }
+  function symbol() public view returns (string memory) {
+    return _symbol;
+  }
+
+  function decimals() public view returns (uint256) {
+    return _decimals;
+  }
+
+  /**
+   * @notice any caller can mint any `_amount`
+   * @param _amount how much to be minted
+   */
+  function mint(uint256 _amount) public {
+    mint(msg.sender, _amount);
+  }
 }

test/contract_spec.js

@@ -20,7 +20,7 @@ config({
   contracts: {
     deploy: {
       "TestToken": {
-        args: [],
+        args: ["TEST", 18],
       },
       "GiftBucket": {
         args: ["$TestToken", EXPIRATION_TIME],