brought tests back

test/utils/FunctionCodec.t.sol

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import { PRBTest } from "@prb/test/PRBTest.sol";
+import { console2 } from "forge-std/console2.sol";
+import { StdCheats } from "forge-std/StdCheats.sol";
+
+import "src/utils/FunctionCodec.sol";
+
+contract FunctionCodecTest is PRBTest, StdCheats {
+    function mockCallback(address, address, IERC20, uint256, uint256, bytes memory) external pure returns(bytes memory) {
+        return "Hello, world!";
+     }
+
+    function testEncodeParams() public {
+        assertEq(
+            FunctionCodec.encodeParams(address(this), this.mockCallback.selector),
+            bytes24(abi.encodePacked(address(this), this.mockCallback.selector))
+        );
+    }
+
+    function testDecodeParams() public {
+        bytes24 encoded = FunctionCodec.encodeParams(address(this), this.mockCallback.selector);
+        (address contractAddr, bytes4 selector) = FunctionCodec.decodeParams(encoded);
+        assertEq(contractAddr, address(this));
+        assertEq(selector, this.mockCallback.selector);
+    }
+
+    function testEncodeFunction() public {
+        bytes24 encoded = FunctionCodec.encodeFunction(this.mockCallback);
+        assertEq(encoded, bytes24(abi.encodePacked(address(this), this.mockCallback.selector)));
+    }
+
+    function testDecodeFunction() public {
+        function(address, address, IERC20, uint256, uint256, bytes memory) external returns (bytes memory) f = FunctionCodec.decodeFunction(address(this), this.mockCallback.selector);
+
+        address a = address(1);
+        IERC20 i = IERC20(a);
+        uint256 u = 1;
+        bytes memory b = "1";
+        assertEq(f(a, a, i, u, u, b), this.mockCallback(a, a, i, u, u, b));
+    }
+
+    function testDecodeFunction2() public {
+        bytes24 encoded = FunctionCodec.encodeFunction(this.mockCallback);
+        function(address, address, IERC20, uint256, uint256, bytes memory) external returns (bytes memory) f = FunctionCodec.decodeFunction(encoded);
+
+        address a = address(1);
+        IERC20 i = IERC20(a);
+        uint256 u = 1;
+        bytes memory b = "1";
+        assertEq(f(a, a, i, u, u, b), this.mockCallback(a, a, i, u, u, b));
+    }
+}