--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang-tools-extra/clangd/unittests/FeatureModulesTests.cpp	Tue Jun 15 19:15:29 2021 +0900
@@ -0,0 +1,58 @@
+//===--- FeatureModulesTests.cpp  -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "FeatureModule.h"
+#include "Selection.h"
+#include "TestTU.h"
+#include "refactor/Tweak.h"
+#include "support/Logger.h"
+#include "llvm/Support/Error.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <memory>
+
+namespace clang {
+namespace clangd {
+namespace {
+
+TEST(FeatureModulesTest, ContributesTweak) {
+  static constexpr const char *TweakID = "ModuleTweak";
+  struct TweakContributingModule final : public FeatureModule {
+    struct ModuleTweak final : public Tweak {
+      const char *id() const override { return TweakID; }
+      bool prepare(const Selection &Sel) override { return true; }
+      Expected<Effect> apply(const Selection &Sel) override {
+        return error("not implemented");
+      }
+      std::string title() const override { return id(); }
+      llvm::StringLiteral kind() const override {
+        return llvm::StringLiteral("");
+      };
+    };
+
+    void contributeTweaks(std::vector<std::unique_ptr<Tweak>> &Out) override {
+      Out.emplace_back(new ModuleTweak);
+    }
+  };
+
+  FeatureModuleSet Set;
+  Set.add(std::make_unique<TweakContributingModule>());
+
+  auto AST = TestTU::withCode("").build();
+  auto Tree =
+      SelectionTree::createRight(AST.getASTContext(), AST.getTokens(), 0, 0);
+  auto Actual = prepareTweak(
+      TweakID, Tweak::Selection(nullptr, AST, 0, 0, std::move(Tree), nullptr),
+      &Set);
+  ASSERT_TRUE(bool(Actual));
+  EXPECT_EQ(Actual->get()->id(), TweakID);
+}
+
+} // namespace
+} // namespace clangd
+} // namespace clang