diff --git a/.clang-tidy b/.clang-tidy
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -6,6 +6,10 @@
     value:           CamelCase
   - key:             readability-identifier-naming.FunctionCase
     value:           camelBack
+  # Exclude from scanning as this is an exported symbol used for fuzzing
+  # throughout the code base.
+  - key:             readability-identifier-naming.FunctionIgnoredRegexp
+    value:           "LLVMFuzzerTestOneInput"
   - key:             readability-identifier-naming.MemberCase
     value:           CamelCase
   - key:             readability-identifier-naming.ParameterCase
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -71,8 +71,8 @@
   return llvm::None;
 }
 
-const llvm::StringLiteral APPLY_FIX_COMMAND = "clangd.applyFix";
-const llvm::StringLiteral APPLY_TWEAK_COMMAND = "clangd.applyTweak";
+const llvm::StringLiteral ApplyFixCommand = "clangd.applyFix";
+const llvm::StringLiteral ApplyTweakCommand = "clangd.applyTweak";
 
 /// Transforms a tweak into a code action that would apply it if executed.
 /// EXPECTS: T.prepare() was called and returned true.
@@ -88,7 +88,7 @@
   //        directly.
   CA.command.emplace();
   CA.command->title = T.Title;
-  CA.command->command = std::string(APPLY_TWEAK_COMMAND);
+  CA.command->command = std::string(ApplyTweakCommand);
   TweakArgs Args;
   Args.file = File;
   Args.tweakID = T.ID;
@@ -950,7 +950,7 @@
   if (Action.command) {
     Cmd = *Action.command;
   } else if (Action.edit) {
-    Cmd.command = std::string(APPLY_FIX_COMMAND);
+    Cmd.command = std::string(ApplyFixCommand);
     Cmd.argument = *Action.edit;
   } else {
     return None;
@@ -1495,8 +1495,8 @@
   Bind.method("$/memoryUsage", this, &ClangdLSPServer::onMemoryUsage);
   if (Opts.FoldingRanges)
     Bind.method("textDocument/foldingRange", this, &ClangdLSPServer::onFoldingRange);
-  Bind.command(APPLY_FIX_COMMAND, this, &ClangdLSPServer::onCommandApplyEdit);
-  Bind.command(APPLY_TWEAK_COMMAND, this, &ClangdLSPServer::onCommandApplyTweak);
+  Bind.command(ApplyFixCommand, this, &ClangdLSPServer::onCommandApplyEdit);
+  Bind.command(ApplyTweakCommand, this, &ClangdLSPServer::onCommandApplyTweak);
 
   ApplyWorkspaceEdit = Bind.outgoingMethod("workspace/applyEdit");
   PublishDiagnostics = Bind.outgoingNotification("textDocument/publishDiagnostics");
diff --git a/clang-tools-extra/clangd/SourceCode.cpp b/clang-tools-extra/clangd/SourceCode.cpp
--- a/clang-tools-extra/clangd/SourceCode.cpp
+++ b/clang-tools-extra/clangd/SourceCode.cpp
@@ -1177,10 +1177,10 @@
     return false;
   auto FID = SM.getFileID(Loc);
   // All proto generated headers should start with this line.
-  static const char *PROTO_HEADER_COMMENT =
+  static const char *ProtoHeaderComment =
       "// Generated by the protocol buffer compiler.  DO NOT EDIT!";
   // Double check that this is an actual protobuf header.
-  return SM.getBufferData(FID).startswith(PROTO_HEADER_COMMENT);
+  return SM.getBufferData(FID).startswith(ProtoHeaderComment);
 }
 
 namespace {
diff --git a/clang-tools-extra/clangd/TUScheduler.cpp b/clang-tools-extra/clangd/TUScheduler.cpp
--- a/clang-tools-extra/clangd/TUScheduler.cpp
+++ b/clang-tools-extra/clangd/TUScheduler.cpp
@@ -100,10 +100,10 @@
 class ASTWorker;
 } // namespace
 
-static clang::clangd::Key<std::string> kFileBeingProcessed;
+static clang::clangd::Key<std::string> KFileBeingProcessed;
 
 llvm::Optional<llvm::StringRef> TUScheduler::getFileBeingProcessedInContext() {
-  if (auto *File = Context::current().get(kFileBeingProcessed))
+  if (auto *File = Context::current().get(KFileBeingProcessed))
     return llvm::StringRef(*File);
   return None;
 }
@@ -1228,7 +1228,7 @@
     }
 
     // Allow this request to be cancelled if invalidated.
-    Context Ctx = Context::current().derive(kFileBeingProcessed, FileName);
+    Context Ctx = Context::current().derive(KFileBeingProcessed, FileName);
     Canceler Invalidate = nullptr;
     if (Invalidation) {
       WithContext WC(std::move(Ctx));
@@ -1656,7 +1656,7 @@
   auto Task = [Worker, Consistency, Name = Name.str(), File = File.str(),
                Contents = It->second->Contents,
                Command = Worker->getCurrentCompileCommand(),
-               Ctx = Context::current().derive(kFileBeingProcessed,
+               Ctx = Context::current().derive(KFileBeingProcessed,
                                                std::string(File)),
                Action = std::move(Action), this]() mutable {
     ThreadCrashReporter ScopedReporter([&Name, &Contents, &Command]() {
diff --git a/clang-tools-extra/clangd/XRefs.cpp b/clang-tools-extra/clangd/XRefs.cpp
--- a/clang-tools-extra/clangd/XRefs.cpp
+++ b/clang-tools-extra/clangd/XRefs.cpp
@@ -1861,7 +1861,7 @@
       QualType VisitCXXThrowExpr(const CXXThrowExpr *S) {
         return S->getSubExpr()->getType();
       }
-      QualType VisitCoyieldStmt(const CoyieldExpr *S) {
+      QualType visitCoyieldStmt(const CoyieldExpr *S) {
         return type(S->getOperand());
       }
       // Treat a designated initializer like a reference to the field.
diff --git a/clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp b/clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
--- a/clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
+++ b/clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
@@ -73,29 +73,29 @@
   return Requests;
 }
 
-static void MemQueries(benchmark::State &State) {
+static void memQueries(benchmark::State &State) {
   const auto Mem = buildMem();
   const auto Requests = extractQueriesFromLogs();
   for (auto _ : State)
     for (const auto &Request : Requests)
       Mem->fuzzyFind(Request, [](const Symbol &S) {});
 }
-BENCHMARK(MemQueries);
+BENCHMARK(memQueries);
 
-static void DexQueries(benchmark::State &State) {
+static void dexQueries(benchmark::State &State) {
   const auto Dex = buildDex();
   const auto Requests = extractQueriesFromLogs();
   for (auto _ : State)
     for (const auto &Request : Requests)
       Dex->fuzzyFind(Request, [](const Symbol &S) {});
 }
-BENCHMARK(DexQueries);
+BENCHMARK(dexQueries);
 
-static void DexBuild(benchmark::State &State) {
+static void dexBuild(benchmark::State &State) {
   for (auto _ : State)
     buildDex();
 }
-BENCHMARK(DexBuild);
+BENCHMARK(dexBuild);
 
 } // namespace
 } // namespace clangd
diff --git a/clang-tools-extra/clangd/fuzzer/clangd-fuzzer.cpp b/clang-tools-extra/clangd/fuzzer/clangd-fuzzer.cpp
--- a/clang-tools-extra/clangd/fuzzer/clangd-fuzzer.cpp
+++ b/clang-tools-extra/clangd/fuzzer/clangd-fuzzer.cpp
@@ -19,12 +19,12 @@
 
 using namespace clang::clangd;
 
-extern "C" int LLVMFuzzerTestOneInput(uint8_t *data, size_t size) {
-  if (size == 0)
+extern "C" int LLVMFuzzerTestOneInput(uint8_t *Data, size_t Size) {
+  if (Size == 0)
     return 0;
 
   // fmemopen isn't portable, but I think we only run the fuzzer on Linux.
-  std::FILE *In = fmemopen(data, size, "r");
+  std::FILE *In = fmemopen(Data, Size, "r");
   auto Transport = newJSONTransport(In, llvm::nulls(),
                                     /*InMirror=*/nullptr, /*Pretty=*/false,
                                     /*Style=*/JSONStreamStyle::Delimited);
diff --git a/clang-tools-extra/clangd/index/YAMLSerialization.cpp b/clang-tools-extra/clangd/index/YAMLSerialization.cpp
--- a/clang-tools-extra/clangd/index/YAMLSerialization.cpp
+++ b/clang-tools-extra/clangd/index/YAMLSerialization.cpp
@@ -161,19 +161,19 @@
 };
 
 template <> struct MappingTraits<SymbolInfo> {
-  static void mapping(IO &io, SymbolInfo &SymInfo) {
+  static void mapping(IO &Io, SymbolInfo &SymInfo) {
     // FIXME: expose other fields?
-    io.mapRequired("Kind", SymInfo.Kind);
-    io.mapRequired("Lang", SymInfo.Lang);
+    Io.mapRequired("Kind", SymInfo.Kind);
+    Io.mapRequired("Lang", SymInfo.Lang);
   }
 };
 
 template <>
 struct MappingTraits<clang::clangd::Symbol::IncludeHeaderWithReferences> {
-  static void mapping(IO &io,
+  static void mapping(IO &Io,
                       clang::clangd::Symbol::IncludeHeaderWithReferences &Inc) {
-    io.mapRequired("Header", Inc.IncludeHeader);
-    io.mapRequired("References", Inc.References);
+    Io.mapRequired("Header", Inc.IncludeHeader);
+    Io.mapRequired("References", Inc.References);
   }
 };
 
diff --git a/clang-tools-extra/clangd/unittests/BackgroundIndexTests.cpp b/clang-tools-extra/clangd/unittests/BackgroundIndexTests.cpp
--- a/clang-tools-extra/clangd/unittests/BackgroundIndexTests.cpp
+++ b/clang-tools-extra/clangd/unittests/BackgroundIndexTests.cpp
@@ -36,6 +36,7 @@
 MATCHER(Defined, "") { return !StringRef(arg.Definition.FileURI).empty(); }
 MATCHER_P(FileURI, F, "") { return StringRef(arg.Location.FileURI) == F; }
 ::testing::Matcher<const RefSlab &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 RefsAre(std::vector<::testing::Matcher<Ref>> Matchers) {
   return ElementsAre(::testing::Pair(_, UnorderedElementsAreArray(Matchers)));
 }
@@ -270,7 +271,6 @@
       void f_b();
       class A_CC {};
       )cpp";
-  std::string A_CC = "";
   FS.Files[testPath("root/A.cc")] = R"cpp(
       #include "A.h"
       void g() { (void)common; }
@@ -344,8 +344,8 @@
       void f_b();
       class A_CC {};
       )cpp";
-  std::string A_CC = "#include \"A.h\"\nvoid g() { (void)common; }";
-  FS.Files[testPath("root/A.cc")] = A_CC;
+  FS.Files[testPath("root/A.cc")] =
+      "#include \"A.h\"\nvoid g() { (void)common; }";
 
   llvm::StringMap<std::string> Storage;
   size_t CacheHits = 0;
diff --git a/clang-tools-extra/clangd/unittests/CallHierarchyTests.cpp b/clang-tools-extra/clangd/unittests/CallHierarchyTests.cpp
--- a/clang-tools-extra/clangd/unittests/CallHierarchyTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CallHierarchyTests.cpp
@@ -56,10 +56,12 @@
 MATCHER_P(WithSelectionRange, R, "") { return arg.selectionRange == R; }
 
 template <class ItemMatcher>
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<CallHierarchyIncomingCall> From(ItemMatcher M) {
   return Field(&CallHierarchyIncomingCall::from, M);
 }
 template <class... RangeMatchers>
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<CallHierarchyIncomingCall> FromRanges(RangeMatchers... M) {
   return Field(&CallHierarchyIncomingCall::fromRanges,
                UnorderedElementsAre(M...));
diff --git a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
--- a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -84,9 +84,11 @@
 MATCHER_P(Signature, S, "") { return arg.Signature == S; }
 
 // Shorthand for Contains(Named(Name)).
+// NOLINTNEXTLINE(readability-identifier-naming)
 Matcher<const std::vector<CodeCompletion> &> Has(std::string Name) {
   return Contains(Named(std::move(Name)));
 }
+// NOLINTNEXTLINE(readability-identifier-naming)
 Matcher<const std::vector<CodeCompletion> &> Has(std::string Name,
                                                  CompletionItemKind K) {
   return Contains(AllOf(Named(std::move(Name)), Kind(K)));
@@ -1230,6 +1232,7 @@
 
 /// \p AnnotatedLabel is a signature label with ranges marking parameters, e.g.
 ///    foo([[int p1]], [[double p2]]) -> void
+// NOLINTNEXTLINE(readability-identifier-naming)
 Matcher<SignatureInformation> Sig(llvm::StringRef AnnotatedLabel) {
   llvm::Annotations A(AnnotatedLabel);
   std::string Label = std::string(A.code());
diff --git a/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp b/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
--- a/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
@@ -22,6 +22,7 @@
 namespace clang {
 namespace clangd {
 namespace config {
+// NOLINTNEXTLINE(readability-identifier-naming)
 template <typename T> void PrintTo(const Located<T> &V, std::ostream *OS) {
   *OS << ::testing::PrintToString(*V);
 }
diff --git a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
--- a/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp
@@ -44,27 +44,32 @@
 using ::testing::UnorderedElementsAre;
 using testing::UnorderedElementsAreArray;
 
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<const Diag &> WithFix(::testing::Matcher<Fix> FixMatcher) {
   return Field(&Diag::Fixes, ElementsAre(FixMatcher));
 }
 
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<const Diag &> WithFix(::testing::Matcher<Fix> FixMatcher1,
                                          ::testing::Matcher<Fix> FixMatcher2) {
   return Field(&Diag::Fixes, UnorderedElementsAre(FixMatcher1, FixMatcher2));
 }
 
 ::testing::Matcher<const Diag &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 WithNote(::testing::Matcher<Note> NoteMatcher) {
   return Field(&Diag::Notes, ElementsAre(NoteMatcher));
 }
 
 ::testing::Matcher<const Diag &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 WithNote(::testing::Matcher<Note> NoteMatcher1,
          ::testing::Matcher<Note> NoteMatcher2) {
   return Field(&Diag::Notes, UnorderedElementsAre(NoteMatcher1, NoteMatcher2));
 }
 
 ::testing::Matcher<const Diag &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 WithTag(::testing::Matcher<DiagnosticTag> TagMatcher) {
   return Field(&Diag::Tags, Contains(TagMatcher));
 }
@@ -114,10 +119,10 @@
 }
 
 // Helper function to make tests shorter.
-Position pos(int line, int character) {
+Position pos(int Line, int Character) {
   Position Res;
-  Res.line = line;
-  Res.character = character;
+  Res.line = Line;
+  Res.character = Character;
   return Res;
 }
 
diff --git a/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp b/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
--- a/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
+++ b/clang-tools-extra/clangd/unittests/ExpectedTypeTest.cpp
@@ -41,7 +41,7 @@
   /// An overload for convenience.
   llvm::Optional<OpaqueType> fromCompletionResult(const NamedDecl *D) {
     return OpaqueType::fromCompletionResult(
-        ASTCtx(), CodeCompletionResult(D, CCP_Declaration));
+        astCtx(), CodeCompletionResult(D, CCP_Declaration));
   }
 
   /// A set of DeclNames whose type match each other computed by
@@ -49,6 +49,7 @@
   using EquivClass = std::set<std::string>;
 
   Matcher<std::map<std::string, EquivClass>>
+  // NOLINTNEXTLINE(readability-identifier-naming)
   ClassesAre(llvm::ArrayRef<EquivClass> Classes) {
     using MapEntry = std::map<std::string, EquivClass>::value_type;
 
@@ -65,13 +66,13 @@
   buildEquivClasses(llvm::ArrayRef<llvm::StringRef> DeclNames) {
     std::map<std::string, EquivClass> Classes;
     for (llvm::StringRef Name : DeclNames) {
-      auto Type = OpaqueType::fromType(ASTCtx(), typeOf(Name));
+      auto Type = OpaqueType::fromType(astCtx(), typeOf(Name));
       Classes[std::string(Type->raw())].insert(std::string(Name));
     }
     return Classes;
   }
 
-  ASTContext &ASTCtx() { return AST->getASTContext(); }
+  ASTContext &astCtx() { return AST->getASTContext(); }
 
 private:
   // Set after calling build().
@@ -140,10 +141,10 @@
      int* int_ptr;
   )cpp");
 
-  OpaqueType IntTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_"));
+  OpaqueType IntTy = *OpaqueType::fromType(astCtx(), typeOf("int_"));
   EXPECT_EQ(fromCompletionResult(decl("returns_int")), IntTy);
 
-  OpaqueType IntPtrTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_ptr"));
+  OpaqueType IntPtrTy = *OpaqueType::fromType(astCtx(), typeOf("int_ptr"));
   EXPECT_EQ(fromCompletionResult(decl("returns_ptr")), IntPtrTy);
 }
 
@@ -162,7 +163,7 @@
 int* int_ptr_;
   )cpp");
 
-  auto IntPtrTy = *OpaqueType::fromType(ASTCtx(), typeOf("int_ptr_"));
+  auto IntPtrTy = *OpaqueType::fromType(astCtx(), typeOf("int_ptr_"));
   EXPECT_EQ(fromCompletionResult(decl("returns_not_dependent")), IntPtrTy);
   EXPECT_EQ(fromCompletionResult(decl("returns_dependent")), llvm::None);
 
diff --git a/clang-tools-extra/clangd/unittests/FileIndexTests.cpp b/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
--- a/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FileIndexTests.cpp
@@ -67,6 +67,7 @@
 namespace clangd {
 namespace {
 ::testing::Matcher<const RefSlab &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 RefsAre(std::vector<::testing::Matcher<Ref>> Matchers) {
   return ElementsAre(::testing::Pair(_, UnorderedElementsAreArray(Matchers)));
 }
@@ -80,8 +81,8 @@
 
 std::unique_ptr<SymbolSlab> numSlab(int Begin, int End) {
   SymbolSlab::Builder Slab;
-  for (int i = Begin; i <= End; i++)
-    Slab.insert(symbol(std::to_string(i)));
+  for (int I = Begin; I <= End; I++)
+    Slab.insert(symbol(std::to_string(I)));
   return std::make_unique<SymbolSlab>(std::move(Slab).build());
 }
 
diff --git a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
--- a/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/FindSymbolsTests.cpp
@@ -41,6 +41,7 @@
 // GMock helpers for matching DocumentSymbol.
 MATCHER_P(SymNameRange, Range, "") { return arg.selectionRange == Range; }
 template <class... ChildMatchers>
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<DocumentSymbol> Children(ChildMatchers... ChildrenM) {
   return Field(&DocumentSymbol::children, UnorderedElementsAre(ChildrenM...));
 }
diff --git a/clang-tools-extra/clangd/unittests/HeadersTests.cpp b/clang-tools-extra/clangd/unittests/HeadersTests.cpp
--- a/clang-tools-extra/clangd/unittests/HeadersTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HeadersTests.cpp
@@ -445,20 +445,20 @@
   )cpp");
 
   auto AST = TU.build();
-  auto &vector_nonstd = findDecl(AST, "vector");
-  auto *vec =
+  auto &VectorNonstd = findDecl(AST, "vector");
+  auto *Vec =
       cast<VarDecl>(findDecl(AST, "vec")).getType()->getAsCXXRecordDecl();
-  auto *nest =
+  auto *Nest =
       cast<VarDecl>(findDecl(AST, "nest")).getType()->getAsCXXRecordDecl();
-  auto *sec =
+  auto *Sec =
       cast<VarDecl>(findDecl(AST, "sec")).getType()->getAsCXXRecordDecl();
 
-  stdlib::Recognizer recognizer;
+  stdlib::Recognizer Recognizer;
 
-  EXPECT_EQ(recognizer(&vector_nonstd), llvm::None);
-  EXPECT_EQ(recognizer(vec), stdlib::Symbol::named("std::", "vector"));
-  EXPECT_EQ(recognizer(nest), stdlib::Symbol::named("std::", "vector"));
-  EXPECT_EQ(recognizer(sec), llvm::None);
+  EXPECT_EQ(Recognizer(&VectorNonstd), llvm::None);
+  EXPECT_EQ(Recognizer(Vec), stdlib::Symbol::named("std::", "vector"));
+  EXPECT_EQ(Recognizer(Nest), stdlib::Symbol::named("std::", "vector"));
+  EXPECT_EQ(Recognizer(Sec), llvm::None);
 }
 
 } // namespace
diff --git a/clang-tools-extra/clangd/unittests/IndexActionTests.cpp b/clang-tools-extra/clangd/unittests/IndexActionTests.cpp
--- a/clang-tools-extra/clangd/unittests/IndexActionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/IndexActionTests.cpp
@@ -40,6 +40,7 @@
 }
 
 ::testing::Matcher<const IncludeGraphNode &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 IncludesAre(const std::vector<std::string> &Includes) {
   return ::testing::Field(&IncludeGraphNode::DirectIncludes,
                           UnorderedPointwise(HasSameURI(), Includes));
diff --git a/clang-tools-extra/clangd/unittests/JSONTransportTests.cpp b/clang-tools-extra/clangd/unittests/JSONTransportTests.cpp
--- a/clang-tools-extra/clangd/unittests/JSONTransportTests.cpp
+++ b/clang-tools-extra/clangd/unittests/JSONTransportTests.cpp
@@ -40,7 +40,7 @@
 
   std::string input() const { return InBuf; }
   std::string output() { return Out.str(); }
-  std::string input_mirror() { return Mirror.str(); }
+  std::string inputMirror() { return Mirror.str(); }
 };
 
 // Echo is a simple server running on a transport:
@@ -129,7 +129,7 @@
       "Content-Length: 77\r\n\r\n"
       R"({"error":{"code":88,"message":"trouble at mill"},"id":"wxyz","jsonrpc":"2.0"})";
   EXPECT_EQ(output(), WantOutput);
-  EXPECT_EQ(trim(input_mirror()), trim(input()));
+  EXPECT_EQ(trim(inputMirror()), trim(input()));
 }
 
 // Runs an Echo session using the "delimited" input and pretty-printed output
@@ -185,7 +185,7 @@
   "jsonrpc": "2.0"
 })";
   EXPECT_EQ(output(), WantOutput);
-  EXPECT_EQ(trim(input_mirror()), trim(input()));
+  EXPECT_EQ(trim(inputMirror()), trim(input()));
 }
 
 // IO errors such as EOF ane reported.
@@ -199,7 +199,7 @@
   EXPECT_EQ(trim(E.log()), "Notification call: 1234");
   EXPECT_TRUE(bool(Err)); // Ran into EOF with no handler signalling done.
   consumeError(std::move(Err));
-  EXPECT_EQ(trim(input_mirror()), trim(input()));
+  EXPECT_EQ(trim(inputMirror()), trim(input()));
 }
 
 #endif
diff --git a/clang-tools-extra/clangd/unittests/QualityTests.cpp b/clang-tools-extra/clangd/unittests/QualityTests.cpp
--- a/clang-tools-extra/clangd/unittests/QualityTests.cpp
+++ b/clang-tools-extra/clangd/unittests/QualityTests.cpp
@@ -139,7 +139,7 @@
   EXPECT_FLOAT_EQ(Relevance.SemaFileProximityScore, 1.0f)
       << "Current file and header";
 
-  auto constructShadowDeclCompletionResult = [&](const std::string DeclName) {
+  auto ConstructShadowDeclCompletionResult = [&](const std::string DeclName) {
     auto *Shadow =
         *dyn_cast<UsingDecl>(&findDecl(AST, [&](const NamedDecl &ND) {
            if (const UsingDecl *Using = dyn_cast<UsingDecl>(&ND))
@@ -154,10 +154,10 @@
   };
 
   Relevance = {};
-  Relevance.merge(constructShadowDeclCompletionResult("Bar"));
+  Relevance.merge(ConstructShadowDeclCompletionResult("Bar"));
   EXPECT_FLOAT_EQ(Relevance.SemaFileProximityScore, 1.0f)
       << "Using declaration in main file";
-  Relevance.merge(constructShadowDeclCompletionResult("FLAGS_FOO"));
+  Relevance.merge(ConstructShadowDeclCompletionResult("FLAGS_FOO"));
   EXPECT_FLOAT_EQ(Relevance.SemaFileProximityScore, 1.0f)
       << "Using declaration in main file";
 
diff --git a/clang-tools-extra/clangd/unittests/SerializationTests.cpp b/clang-tools-extra/clangd/unittests/SerializationTests.cpp
--- a/clang-tools-extra/clangd/unittests/SerializationTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SerializationTests.cpp
@@ -194,12 +194,15 @@
   EXPECT_EQ(IGNDeserialized.Flags, IncludeGraphNode::SourceFlag(1));
 }
 
+// NOLINTNEXTLINE(readability-identifier-naming)
 std::vector<std::string> YAMLFromSymbols(const SymbolSlab &Slab) {
   std::vector<std::string> Result;
   for (const auto &Sym : Slab)
     Result.push_back(toYAML(Sym));
   return Result;
 }
+
+// NOLINTNEXTLINE(readability-identifier-naming)
 std::vector<std::string> YAMLFromRefs(const RefSlab &Slab) {
   std::vector<std::string> Result;
   for (const auto &Refs : Slab)
@@ -207,6 +210,7 @@
   return Result;
 }
 
+// NOLINTNEXTLINE(readability-identifier-naming)
 std::vector<std::string> YAMLFromRelations(const RelationSlab &Slab) {
   std::vector<std::string> Result;
   for (const auto &Rel : Slab)
diff --git a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
--- a/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp
@@ -101,6 +101,7 @@
   return arg == Relation{Subject.ID, RelationKind::OverriddenBy, Object.ID};
 }
 ::testing::Matcher<const std::vector<Ref> &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 HaveRanges(const std::vector<Range> Ranges) {
   return ::testing::UnorderedPointwise(RefRange(), Ranges);
 }
diff --git a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
--- a/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SymbolInfoTests.cpp
@@ -26,10 +26,10 @@
 
 using ::testing::UnorderedElementsAreArray;
 
-auto CreateExpectedSymbolDetails = [](const std::string &name,
-                                      const std::string &container,
+auto CreateExpectedSymbolDetails = [](const std::string &Name,
+                                      const std::string &Container,
                                       const std::string &USR) {
-  return SymbolDetails{name, container, USR, SymbolID(USR)};
+  return SymbolDetails{Name, Container, USR, SymbolID(USR)};
 };
 
 TEST(SymbolInfoTests, All) {
diff --git a/clang-tools-extra/clangd/unittests/TestIndex.cpp b/clang-tools-extra/clangd/unittests/TestIndex.cpp
--- a/clang-tools-extra/clangd/unittests/TestIndex.cpp
+++ b/clang-tools-extra/clangd/unittests/TestIndex.cpp
@@ -86,8 +86,8 @@
 
 SymbolSlab generateNumSymbols(int Begin, int End) {
   std::vector<std::string> Names;
-  for (int i = Begin; i <= End; i++)
-    Names.push_back(std::to_string(i));
+  for (int I = Begin; I <= End; I++)
+    Names.push_back(std::to_string(I));
   return generateSymbols(Names);
 }
 
diff --git a/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp b/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
--- a/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TypeHierarchyTests.cpp
@@ -39,11 +39,13 @@
 MATCHER_P(WithKind, Kind, "") { return arg.kind == Kind; }
 MATCHER_P(SelectionRangeIs, R, "") { return arg.selectionRange == R; }
 template <class... ParentMatchers>
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<TypeHierarchyItem> Parents(ParentMatchers... ParentsM) {
   return Field(&TypeHierarchyItem::parents,
                HasValue(UnorderedElementsAre(ParentsM...)));
 }
 template <class... ChildMatchers>
+// NOLINTNEXTLINE(readability-identifier-naming)
 ::testing::Matcher<TypeHierarchyItem> Children(ChildMatchers... ChildrenM) {
   return Field(&TypeHierarchyItem::children,
                HasValue(UnorderedElementsAre(ChildrenM...)));
diff --git a/clang-tools-extra/clangd/unittests/XRefsTests.cpp b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
--- a/clang-tools-extra/clangd/unittests/XRefsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
@@ -60,6 +60,7 @@
 // Extracts ranges from an annotated example, and constructs a matcher for a
 // highlight set. Ranges should be named $read/$write as appropriate.
 Matcher<const std::vector<DocumentHighlight> &>
+// NOLINTNEXTLINE(readability-identifier-naming)
 HighlightsFrom(const Annotations &Test) {
   std::vector<DocumentHighlight> Expected;
   auto Add = [&](const Range &R, DocumentHighlightKind K) {
diff --git a/clang-tools-extra/clangd/unittests/support/ThreadingTests.cpp b/clang-tools-extra/clangd/unittests/support/ThreadingTests.cpp
--- a/clang-tools-extra/clangd/unittests/support/ThreadingTests.cpp
+++ b/clang-tools-extra/clangd/unittests/support/ThreadingTests.cpp
@@ -29,7 +29,7 @@
   int Counter(0); /* GUARDED_BY(Mutex) */
   {
     AsyncTaskRunner Tasks;
-    auto scheduleIncrements = [&]() {
+    auto ScheduleIncrements = [&]() {
       for (int TaskI = 0; TaskI < TasksCnt; ++TaskI) {
         Tasks.runAsync("task", [&Counter, &Mutex, IncrementsPerTask]() {
           for (int Increment = 0; Increment < IncrementsPerTask; ++Increment) {
@@ -44,7 +44,7 @@
       // Make sure runAsync is not running tasks synchronously on the same
       // thread by locking the Mutex used for increments.
       std::lock_guard<std::mutex> Lock(Mutex);
-      scheduleIncrements();
+      ScheduleIncrements();
     }
 
     Tasks.wait();
@@ -56,7 +56,7 @@
     {
       std::lock_guard<std::mutex> Lock(Mutex);
       Counter = 0;
-      scheduleIncrements();
+      ScheduleIncrements();
     }
   }
   // Check that destructor has waited for tasks to finish.
diff --git a/clang-tools-extra/clangd/unittests/support/TraceTests.cpp b/clang-tools-extra/clangd/unittests/support/TraceTests.cpp
--- a/clang-tools-extra/clangd/unittests/support/TraceTests.cpp
+++ b/clang-tools-extra/clangd/unittests/support/TraceTests.cpp
@@ -39,7 +39,7 @@
 
 // Checks that N is a Mapping (JS object) with the expected scalar properties.
 // The object must have all the Expected properties, but may have others.
-bool VerifyObject(llvm::yaml::Node &N,
+bool VerifyObject(llvm::yaml::Node &N, // NOLINT(readability-identifier-naming)
                   std::map<std::string, std::string> Expected) {
   auto *M = llvm::dyn_cast<llvm::yaml::MappingNode>(&N);
   if (!M) {