citizen: add foundry test suite

test/LabHelper.t.sol

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.24;
+
+import "forge-std/Test.sol";
+import "../contracts/LabHelper.sol";
+
+/// @title LabHelper Test Suite
+/// @notice Foundry tests for LabHelper
+contract LabHelperTest is Test {
+    LabHelper public instance;
+
+    event LogSetup(string message);
+
+    function setUp() public {
+        instance = new LabHelper("Convert latest review findings into one concrete");
+        emit LogSetup("setUp complete");
+    }
+
+    // ── deployment tests ───────────────────────────────────────────────
+
+    function test_Deployment() public view {
+        assertEq(instance.topic(), "Convert latest review findings into one concrete", "initial topic mismatch");
+    }
+
+    function test_DeploymentNonEmpty() public view {
+        assertTrue(bytes(instance.topic()).length > 0, "topic should not be empty");
+    }
+
+    // ── state mutation tests ───────────────────────────────────────────
+
+    function test_SetTopic() public {
+        string memory next = "updated value";
+        instance.setTopic(next);
+        assertEq(instance.topic(), next, "setTopic failed");
+    }
+
+    function test_SetTopicEmpty() public {
+        instance.setTopic("");
+        assertEq(instance.topic(), "", "setting empty topic failed");
+    }
+
+    function test_SetTopicTwice() public {
+        instance.setTopic("first");
+        instance.setTopic("second");
+        assertEq(instance.topic(), "second", "double set failed");
+    }
+
+    // ── fuzz tests ────────────────────────────────────────────────────
+
+    function testFuzz_SetTopic(string calldata newTopic) public {
+        instance.setTopic(newTopic);
+        assertEq(instance.topic(), newTopic, "fuzz setTopic mismatch");
+    }
+
+    // ── gas benchmarks ────────────────────────────────────────────────
+
+    function test_SetTopicGas() public {
+        uint256 gasBefore = gasleft();
+        instance.setTopic("gas benchmark");
+        uint256 gasUsed = gasBefore - gasleft();
+        assertTrue(gasUsed < 100_000, "setTopic gas too high");
+    }
+}