added dummy implementation

contracts/example/dummyImplementation.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+contract UserModule {
+    /**
+     * @dev User function to supply.
+     * @param amount_ amount to supply.
+     */
+    function supply(uint256 amount_) external {}
+
+    /**
+     * @dev User function to withdraw.
+     * @param amount_ amount to withdraw.
+     */
+    function withdraw(uint256 amount_) external {}
+}
+
+contract ReadModule {
+    /**
+     * @dev Read function to get user's balance in the contract.
+     * @param user_ address of user.
+     */
+    function userBalance(address user_) public view returns (uint256) {}
+}
+
+contract DummyImplementation is UserModule, ReadModule {}