improve universal and libraries tests and coverage

packages/contracts-bedrock/test/libraries/Encoding.t.sol

@@ -71,6 +71,18 @@ contract Encoding_Test is CommonTest {
         assertEq(legacyEncoding, bedrockEncoding);
     }
 
+    /// @dev Tests that encodeCrossDomainMessage reverts if version is greater than 1.
+    function testFuzz_encodeCrossDomainMessage_versionGreaterThanOne_reverts(uint256 nonce) external {
+        // nonce >> 240 must be greater than 1
+        uint256 minInvalidNonce = (uint256(type(uint240).max) + 1) * 2;
+        nonce = bound(nonce, minInvalidNonce, type(uint256).max);
+
+        EncodingContract encoding = new EncodingContract();
+
+        vm.expectRevert(bytes("Encoding: unknown cross domain message version"));
+        encoding.encodeCrossDomainMessage(nonce, address(this), address(this), 1, 100, hex"");
+    }
+
     /// @dev Tests deposit transaction encoding.
     function testDiff_encodeDepositTransaction_succeeds(
         address _from,
@@ -94,3 +106,20 @@ contract Encoding_Test is CommonTest {
         assertEq(txn, _txn);
     }
 }
+
+contract EncodingContract {
+    function encodeCrossDomainMessage(
+        uint256 nonce,
+        address sender,
+        address target,
+        uint256 value,
+        uint256 gasLimit,
+        bytes memory data
+    )
+        external
+        pure
+        returns (bytes memory)
+    {
+        return Encoding.encodeCrossDomainMessage(nonce, sender, target, value, gasLimit, data);
+    }
+}

packages/contracts-bedrock/test/universal/SafeSend.t.sol

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.15;
+
+import { SafeSend } from "src/universal/SafeSend.sol";
+import { CommonTest } from "test/setup/CommonTest.sol";
+
+contract SafeSendTest is CommonTest {
+    /// @notice Tests that sending to an EOA succeeds.
+    function test_send_toEOA_succeeds() public {
+        assertNotEq(alice, address(0));
+        assertNotEq(bob, address(0));
+        assertEq(bob.code.length, 0);
+
+        vm.deal(alice, 100 ether);
+
+        uint256 aliceBalanceBefore = alice.balance;
+        uint256 bobBalanceBefore = bob.balance;
+
+        vm.prank(alice);
+        SafeSend safeSend = new SafeSend{ value: 100 ether }(payable(bob));
+
+        assertEq(address(safeSend).code.length, 0);
+        assertEq(address(safeSend).balance, 0);
+        assertEq(alice.balance, aliceBalanceBefore - 100 ether);
+        assertEq(bob.balance, bobBalanceBefore + 100 ether);
+    }
+
+    /// @notice Tests that sending to a contract succeeds without executing the
+    ///         contract's code.
+    function test_send_toContract_succeeds() public {
+        // etch reverting code into bob
+        vm.etch(bob, hex"fe");
+        vm.deal(alice, 100 ether);
+
+        uint256 aliceBalanceBefore = alice.balance;
+        uint256 bobBalanceBefore = bob.balance;
+
+        vm.prank(alice);
+        SafeSend safeSend = new SafeSend{ value: 100 ether }(payable(bob));
+
+        assertEq(address(safeSend).code.length, 0);
+        assertEq(address(safeSend).balance, 0);
+        assertEq(alice.balance, aliceBalanceBefore - 100 ether);
+        assertEq(bob.balance, bobBalanceBefore + 100 ether);
+    }
+}