test: one contract per file (satisfy rainix single-contract gate)

test/lib/LibDescribedByMeta.emitForDescribedAddress.t.sol

@@ -8,18 +8,7 @@ import {IDescribedByMetaV1} from "src/interface/IDescribedByMetaV1.sol";
 import {IMetaBoardV1_2} from "src/interface/unstable/IMetaBoardV1_2.sol";
 import {MetaBoard} from "src/concrete/MetaBoard.sol";
 import {META_MAGIC_NUMBER_V1} from "src/interface/unstable/IMetaV1_2.sol";
-
-contract TestDescribedByMetaV1 is IDescribedByMetaV1 {
-    bytes32 public immutable EXPECTED;
-
-    constructor(bytes memory meta) {
-        EXPECTED = keccak256(meta);
-    }
-
-    function describedByMetaV1() external view override returns (bytes32) {
-        return EXPECTED;
-    }
-}
+import {TestDescribedByMetaV1} from "test/lib/TestDescribedByMetaV1.sol";
 
 contract LibDescribedByMetaEmitForDescribedAddressTest is Test {
     function externalEmitForDescribedAddress(IMetaBoardV1_2 metaboard, IDescribedByMetaV1 described, bytes memory meta)

test/lib/TestDescribedByMetaV1.sol

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: LicenseRef-DCL-1.0
+// SPDX-FileCopyrightText: Copyright (c) 2020 Rain Open Source Software Ltd
+pragma solidity =0.8.25;
+
+import {IDescribedByMetaV1} from "src/interface/IDescribedByMetaV1.sol";
+
+/// @dev Test implementation of `IDescribedByMetaV1` that reports the keccak256
+/// hash of the metadata bytes provided to its constructor.
+contract TestDescribedByMetaV1 is IDescribedByMetaV1 {
+    bytes32 public immutable EXPECTED;
+
+    constructor(bytes memory meta) {
+        EXPECTED = keccak256(meta);
+    }
+
+    function describedByMetaV1() external view override returns (bytes32) {
+        return EXPECTED;
+    }
+}