Inherit asset decimals in ERC4626 (#3639)

contracts/mocks/ERC4626Mock.sol

@@ -4,7 +4,6 @@ pragma solidity ^0.8.0;
 
 import "../token/ERC20/extensions/ERC4626.sol";
 
-// mock class using ERC20
 contract ERC4626Mock is ERC4626 {
     constructor(
         IERC20Metadata asset,
@@ -20,3 +19,42 @@ contract ERC4626Mock is ERC4626 {
         _burn(account, amount);
     }
 }
+
+contract ERC4626DecimalMock is ERC4626Mock {
+    using Math for uint256;
+
+    uint8 private immutable _decimals;
+
+    constructor(
+        IERC20Metadata asset,
+        string memory name,
+        string memory symbol,
+        uint8 decimalsOverride
+    ) ERC4626Mock(asset, name, symbol) {
+        _decimals = decimalsOverride;
+    }
+
+    function decimals() public view virtual override returns (uint8) {
+        return _decimals;
+    }
+
+    function _initialConvertToShares(uint256 assets, Math.Rounding rounding)
+        internal
+        view
+        virtual
+        override
+        returns (uint256 shares)
+    {
+        return assets.mulDiv(10**decimals(), 10**super.decimals(), rounding);
+    }
+
+    function _initialConvertToAssets(uint256 shares, Math.Rounding rounding)
+        internal
+        view
+        virtual
+        override
+        returns (uint256 assets)
+    {
+        return shares.mulDiv(10**super.decimals(), 10**decimals(), rounding);
+    }
+}