feat: make decimals configurable

Author: anna-carroll

README.md

@@ -3,8 +3,9 @@
 A simple ERC20 token utilizing [OpenZeppelin libraries](https://github.com/OpenZeppelin/openzeppelin-contracts). 
 
 - [Burnable](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/extensions/ERC20Burnable.sol)
-- [Ownable](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol), uncapped Minting 
-- otherwise, [generic ERC20](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol) functionality
+- [Ownable Mint](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol), uncapped Minting 
+- Configurable decimals
+- Otherwise, [generic ERC20](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol) functionality
 
 ## Usage
 

src/SimpleERC20.sol

@@ -7,13 +7,21 @@ import {Ownable} from "openzeppelin-contracts/contracts/access/Ownable.sol";
 
 /// @notice A contract deployed to Host chain that allows tokens to enter the rollup.
 contract SimpleERC20 is ERC20Burnable, Ownable {
-    constructor(address initialOwner, string memory name, string memory symbol)
+    uint8 public immutable _decimals;
+
+    constructor(address initialOwner, string memory name, string memory symbol, uint8 _dec)
         Ownable(initialOwner)
         ERC20(name, symbol)
-    {}
+    {
+        _decimals = _dec;
+    }
 
     function mint(address to, uint256 amount) external onlyOwner returns (bool) {
         _mint(to, amount);
         return true;
     }
+
+    function decimals() public view override returns (uint8) {
+        return _decimals;
+    }
 }

test/SimpleERC20.t.sol

@@ -8,7 +8,13 @@ contract CounterTest is Test {
     SimpleERC20 public test;
 
     function setUp() public {
-        test = new SimpleERC20(address(this), "Test Token", "TEST");
+        test = new SimpleERC20(address(this), "Test Token", "TEST", 8);
+    }
+
+    function testMetadata() public view {
+        assertEq(test.name(), "Test Token");
+        assertEq(test.symbol(), "TEST");
+        assertEq(test.decimals(), 8);
     }
 
     function testMint() public {