diff --git a/test/util/lib/LibTestConstants.sol b/test/util/lib/LibTestConstants.sol
new file mode 100644
index 00000000..0f6f428a
--- /dev/null
+++ b/test/util/lib/LibTestConstants.sol
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: CAL
+pragma solidity ^0.8.18;
+
+import "openzeppelin-contracts/contracts/utils/introspection/IERC1820Registry.sol";
+
+/// @dev https://eips.ethereum.org/EIPS/eip-1820#single-use-registry-deployment-account
+IERC1820Registry constant IERC1820_REGISTRY = IERC1820Registry(0x1820a4B7618BdE71Dce8cdc73aAB6C95905faD24);
+
+/// @dev Mocks need to be etched with some bytecode or they cannot even be
+/// called. This is because Solidity first checks the bytecode size before
+/// calling, so it never even gets to the point that mocking logic can intercept
+/// the call. We want all non-mocked calls to revert, so all mocks should be
+/// etched with a revert opcode.
+bytes constant REVERTING_MOCK_BYTECODE = hex"FD";
+
+/// @dev Stub expression bytecode used for testing purposes.
+/// This is a simple bytecode stub that can be used as a placeholder for
+/// expressions with mock initialization in tests. The bytecode is arbitrary
+bytes constant STUB_EXPRESSION_BYTECODE = hex"010000";