Add unit tests for Bitfield.sol

contracts/test/Bitfield.t.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.25;
+
+import {Test} from "forge-std/Test.sol";
+import {console} from "forge-std/console.sol";
+import {BitfieldWrapper} from "./mocks/BitfieldWrapper.sol";
+import {Bitfield} from "../src/utils/Bitfield.sol";
+
+import {stdJson} from "forge-std/StdJson.sol";
+
+contract BitfieldTest is Test {
+    using stdJson for string;
+
+    function testBitfieldSubsampling() public {
+        BitfieldWrapper bw = new BitfieldWrapper();
+
+        string memory json = vm.readFile(string.concat(vm.projectRoot(), "/test/data/beefy-validator-set.json"));
+        uint32 setSize = uint32(json.readUint(".validatorSetSize"));
+        bytes32 root = json.readBytes32(".validatorRoot");
+        uint256[] memory bitSetArray = json.readUintArray(".participants");
+
+        uint256[] memory initialBitField = bw.createBitfield(bitSetArray, setSize);
+        uint256[] memory finalBitfield = bw.subsample(67, initialBitField, 30, setSize);
+
+        uint256 counter = 0;
+        for (uint256 i = 0; i < bitSetArray.length; i++) {
+            if (Bitfield.isSet(finalBitfield, bitSetArray[i])) {
+                counter++;
+            }
+        }
+        assertEq(30, counter);
+        assertEq(Bitfield.countSetBits(finalBitfield), counter);
+    }
+}

contracts/test/mocks/BitfieldWrapper.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity 0.8.25;
+
+import {Bitfield} from "../../src/utils/Bitfield.sol";
+
+contract BitfieldWrapper {
+    function createBitfield(uint256[] calldata bitsToSet, uint256 length)
+        pure
+        public
+        returns (uint256[] memory bitfield)
+    {
+        return Bitfield.createBitfield(bitsToSet, length);
+    }
+
+    function subsample(uint256 seed, uint256[] memory prior, uint256 n, uint256 length) public returns (uint256[] memory bitfield) {
+        return Bitfield.subsample(seed, prior, n, length);
+    }
+}

flake.nix

@@ -54,7 +54,6 @@
                     gopls
                     go-outline
                     gopkgs
-                    gocode-gomod
                     godef
                     golint
                     mage