Imported Upstream version 6.10.0.49

Former-commit-id: 1d6753294b2993e1fbf92de9366bb9544db4189b

external/llvm-project/lldb/unittests/Utility/ConstStringTest.cpp

@@ -0,0 +1,18 @@
+//===-- ConstStringTest.cpp -------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Utility/ConstString.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+
+TEST(ConstStringTest, format_provider) {
+  EXPECT_EQ("foo", llvm::formatv("{0}", ConstString("foo")).str());
+}