add arbitrum receiever unit tests

test/ArbitrumReceiver.t.sol

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+pragma solidity >=0.8.0;
+
+import "forge-std/Test.sol";
+
+import { TargetContractMock } from "test/mocks/TargetContractMock.sol";
+
+import { ArbitrumReceiver } from "src/receivers/ArbitrumReceiver.sol";
+
+contract ArbitrumReceiverTest is Test {
+
+    TargetContractMock target;
+
+    ArbitrumReceiver receiver;
+
+    address sourceAuthority = makeAddr("sourceAuthority");
+    address sourceAuthorityWithOffset;
+    address randomAddress   = makeAddr("randomAddress");
+
+    function setUp() public {
+        target = new TargetContractMock();
+
+        receiver = new ArbitrumReceiver(
+            sourceAuthority,
+            address(target)
+        );
+        unchecked {
+            sourceAuthorityWithOffset = address(uint160(sourceAuthority) + uint160(0x1111000000000000000000000000000000001111));
+        }
+    }
+
+    function test_constructor() public {
+        receiver = new ArbitrumReceiver(
+            sourceAuthority,
+            address(target)
+        );
+
+        assertEq(receiver.l1Authority(), sourceAuthority);
+        assertEq(receiver.target(),      address(target));
+    }
+
+    function test_forward_invalidL1Authority() public {
+        vm.prank(randomAddress);
+        vm.expectRevert("ArbitrumReceiver/invalid-l1Authority");
+        receiver.forward(abi.encodeCall(TargetContractMock.someFunc, ()));
+    }
+
+    function test_forward_invalidL1AuthoritySourceAuthorityNoOffset() public {
+        vm.prank(sourceAuthority);
+        vm.expectRevert("ArbitrumReceiver/invalid-l1Authority");
+        receiver.forward(abi.encodeCall(TargetContractMock.someFunc, ()));
+    }
+
+    function test_forward_success() public {
+        assertEq(target.data(), 0);
+        vm.prank(sourceAuthorityWithOffset);
+        receiver.forward(abi.encodeCall(TargetContractMock.someFunc, ()));
+        assertEq(target.data(), 1);
+    }
+
+    function test_forward_revert() public {
+        vm.prank(sourceAuthorityWithOffset);
+        vm.expectRevert("error");
+        receiver.forward(abi.encodeCall(TargetContractMock.revertFunc, ()));
+    }
+
+}