1 files changed, 18 insertions, 4 deletions
diff --git a/clang/unittests/Format/SortIncludesTest.cpp b/clang/unittests/Format/SortIncludesTest.cpp
index dbe11749572..9e5f2675f08 100644
--- a/clang/unittests/Format/SortIncludesTest.cpp
+++ b/clang/unittests/Format/SortIncludesTest.cpp
@@ -20,8 +20,12 @@ namespace {
 
 class SortIncludesTest : public ::testing::Test {
 protected:
-  std::string sort(llvm::StringRef Code, StringRef FileName = "input.cpp") {
-    std::vector<tooling::Range> Ranges(1, tooling::Range(0, Code.size()));
+  std::vector<tooling::Range> GetCodeRange(StringRef Code) {
+    return std::vector<tooling::Range>(1, tooling::Range(0, Code.size()));
+  }
+
+  std::string sort(StringRef Code, StringRef FileName = "input.cpp") {
+    auto Ranges = GetCodeRange(Code);
     std::string Sorted =
         applyAllReplacements(Code, sortIncludes(Style, Code, Ranges, FileName));
     return applyAllReplacements(Sorted,
@@ -29,8 +33,7 @@ protected:
   }
 
   unsigned newCursor(llvm::StringRef Code, unsigned Cursor) {
-    std::vector<tooling::Range> Ranges(1, tooling::Range(0, Code.size()));
-    sortIncludes(Style, Code, Ranges, "input.cpp", &Cursor);
+    sortIncludes(Style, Code, GetCodeRange(Code), "input.cpp", &Cursor);
     return Cursor;
   }
 
@@ -47,6 +50,17 @@ TEST_F(SortIncludesTest, BasicSorting) {
                  "#include \"b.h\"\n"));
 }
 
+TEST_F(SortIncludesTest, NoReplacementsForValidIncludes) {
+  // Identical #includes have led to a failure with an unstable sort.
+  std::string Code = "#include <a>\n"
+                     "#include <b>\n"
+                     "#include <b>\n"
+                     "#include <b>\n"
+                     "#include <b>\n"
+                     "#include <c>\n";
+  EXPECT_TRUE(sortIncludes(Style, Code, GetCodeRange(Code), "a.cc").empty());
+}
+
 TEST_F(SortIncludesTest, SupportClangFormatOff) {
   EXPECT_EQ("#include <a>\n"
             "#include <b>\n"