diff --git a/src/libs/clangsupport/commandlinebuilder.h b/src/libs/clangsupport/commandlinebuilder.h
index 9b5bced9328..03d042322d9 100644
--- a/src/libs/clangsupport/commandlinebuilder.h
+++ b/src/libs/clangsupport/commandlinebuilder.h
@@ -25,7 +25,7 @@
 
 #pragma once
 
-#include "filepathview.h"
+#include "filepath.h"
 
 #include <compilermacro.h>
 #include <includesearchpath.h>
@@ -35,7 +35,7 @@
 
 namespace ClangBackEnd {
 
-template<typename ProjectInfo, typename OutputContainer = std::vector<std::string>>
+template<typename ProjectInfo, typename OutputContainer = Utils::SmallStringVector>
 class CommandLineBuilder
 {
 public:
@@ -213,7 +213,7 @@ public:
     {
         for (const IncludeSearchPath &path : projectIncludeSearchPaths) {
             commandLine.emplace_back("-I");
-            commandLine.emplace_back(path.path);
+            commandLine.emplace_back(NativeFilePath(FilePathView(path.path)));
         }
     }
 
@@ -228,7 +228,7 @@ public:
         for (const IncludeSearchPath &path : systemIncludeSearchPaths) {
             if (path.type != IncludeSearchPathType::BuiltIn) {
                 commandLine.emplace_back(includeOption(path.type));
-                commandLine.emplace_back(path.path);
+                commandLine.emplace_back(NativeFilePath(FilePathView(path.path)));
             }
         }
     }
@@ -238,7 +238,7 @@ public:
         for (const IncludeSearchPath &path : systemIncludeSearchPaths) {
             if (path.type == IncludeSearchPathType::BuiltIn) {
                 commandLine.emplace_back(includeOption(path.type));
-                commandLine.emplace_back(path.path);
+                commandLine.emplace_back(NativeFilePath(FilePathView(path.path)));
             }
         }
     }
@@ -247,23 +247,24 @@ public:
     {
         if (!outputPath.isEmpty()) {
             commandLine.emplace_back("-o");
-            commandLine.emplace_back(outputPath);
+            commandLine.emplace_back(NativeFilePath(outputPath));
         }
     }
 
     void addSourcePath(FilePathView sourcePath)
     {
         if (!sourcePath.isEmpty())
-            commandLine.emplace_back(sourcePath);
+            commandLine.emplace_back(NativeFilePath(sourcePath));
     }
 
     void addIncludePchPath(FilePathView includePchPath)
     {
+
         if (!includePchPath.isEmpty()) {
             commandLine.emplace_back("-Xclang");
             commandLine.emplace_back("-include-pch");
             commandLine.emplace_back("-Xclang");
-            commandLine.emplace_back(includePchPath);
+            commandLine.emplace_back(NativeFilePath(includePchPath));
         }
     }
 
diff --git a/src/libs/clangsupport/filepath.h b/src/libs/clangsupport/filepath.h
index e08f3f4996b..72076841945 100644
--- a/src/libs/clangsupport/filepath.h
+++ b/src/libs/clangsupport/filepath.h
@@ -28,7 +28,7 @@
 #include "clangsupport_global.h"
 
 #include "filepathview.h"
-#include "filepathview.h"
+#include "nativefilepath.h"
 
 #include <utils/hostosinfo.h>
 #include <utils/smallstringio.h>
@@ -37,6 +37,8 @@
 
 namespace ClangBackEnd {
 
+class NativeFilePath;
+
 class FilePath : public Utils::PathString
 {
     using size_type = Utils::PathString::size_type;
diff --git a/src/libs/clangsupport/nativefilepath.h b/src/libs/clangsupport/nativefilepath.h
index 31b6778ed04..fefaa9c2057 100644
--- a/src/libs/clangsupport/nativefilepath.h
+++ b/src/libs/clangsupport/nativefilepath.h
@@ -26,13 +26,15 @@
 #pragma once
 
 #include "filepathview.h"
-#include "filepathview.h"
+#include "filepath.h"
 
 #include <utils/hostosinfo.h>
 #include <utils/smallstringio.h>
 
 namespace ClangBackEnd {
 
+class FilePath;
+
 class NativeFilePath
 {
     using size_type = Utils::PathString::size_type;
@@ -50,8 +52,13 @@ public:
     NativeFilePath(NativeFilePathView filePathView)
         : m_path(filePathView.toStringView()),
           m_slashIndex(filePathView.slashIndex())
-    {
-    }
+    {}
+
+    explicit NativeFilePath(FilePathView filePathView) { *this = fromFilePath(filePathView); }
+
+    explicit NativeFilePath(const FilePath &filePath)
+        : NativeFilePath{FilePathView{filePath}}
+    {}
 
     template<size_type Size>
     NativeFilePath(const char(&string)[Size]) noexcept
diff --git a/src/libs/utils/smallstringview.h b/src/libs/utils/smallstringview.h
index d821edbf9b8..6052ff8777f 100644
--- a/src/libs/utils/smallstringview.h
+++ b/src/libs/utils/smallstringview.h
@@ -90,8 +90,7 @@ public:
     SmallStringView(const String &string) noexcept
         : m_pointer(string.data()),
           m_size(string.size())
-    {
-    }
+    {}
 
     static
     SmallStringView fromUtf8(const char *const characterPointer)
diff --git a/src/tools/clangpchmanagerbackend/source/pchcreator.cpp b/src/tools/clangpchmanagerbackend/source/pchcreator.cpp
index 777252dece5..4333d5706ac 100644
--- a/src/tools/clangpchmanagerbackend/source/pchcreator.cpp
+++ b/src/tools/clangpchmanagerbackend/source/pchcreator.cpp
@@ -94,10 +94,9 @@ FilePath PchCreator::generatePchFilePath() const
                                           ".pch"}};
 }
 
-std::vector<std::string> PchCreator::generateClangCompilerArguments(
-    const PchTask &pchTask,
-    FilePathView sourceFilePath,
-    FilePathView pchOutputPath)
+Utils::SmallStringVector PchCreator::generateClangCompilerArguments(const PchTask &pchTask,
+                                                                    FilePathView sourceFilePath,
+                                                                    FilePathView pchOutputPath)
 {
     CommandLineBuilder<PchTask> builder{pchTask,
                                         pchTask.toolChainArguments,
@@ -114,10 +113,12 @@ void PchCreator::generatePch(PchTask &&pchTask)
     auto content = generatePchIncludeFileContent(pchTask.includes);
     auto pchOutputPath = generatePchFilePath();
 
-    m_clangTool.addFile(m_environment.pchBuildDirectory().toStdString(),
-                        "dummy.h",
-                        Utils::SmallStringView(content),
-                        generateClangCompilerArguments(pchTask, "dummy.h", pchOutputPath));
+    FilePath headerFilePath{m_environment.pchBuildDirectory().toStdString(), "dummy.h"};
+    Utils::SmallStringVector commandLine = generateClangCompilerArguments(pchTask,
+                                                                          headerFilePath,
+                                                                          pchOutputPath);
+
+    m_clangTool.addFile(std::move(headerFilePath), std::move(content), std::move(commandLine));
 
     bool success = generatePch();
 
diff --git a/src/tools/clangpchmanagerbackend/source/pchcreator.h b/src/tools/clangpchmanagerbackend/source/pchcreator.h
index 1e36e18b6e1..37d0c7c8a1e 100644
--- a/src/tools/clangpchmanagerbackend/source/pchcreator.h
+++ b/src/tools/clangpchmanagerbackend/source/pchcreator.h
@@ -84,7 +84,7 @@ public:
     bool generatePch();
 
     FilePath generatePchFilePath() const;
-    static std::vector<std::string> generateClangCompilerArguments(const PchTask &pchTask,
+    static Utils::SmallStringVector generateClangCompilerArguments(const PchTask &pchTask,
                                                                    FilePathView includePchHeaderPath,
                                                                    FilePathView pchPath);
 
diff --git a/src/tools/clangrefactoringbackend/source/clangquerygatherer.cpp b/src/tools/clangrefactoringbackend/source/clangquerygatherer.cpp
index 21cd0d26e54..42fb7d88bc2 100644
--- a/src/tools/clangrefactoringbackend/source/clangquerygatherer.cpp
+++ b/src/tools/clangrefactoringbackend/source/clangquerygatherer.cpp
@@ -50,10 +50,9 @@ ClangQueryGatherer::createSourceRangesForSource(
 {
     ClangQuery clangQuery(*filePathCache, std::move(query));
 
-    clangQuery.addFile(std::string(source.filePath.directory()),
-                       std::string(source.filePath.name()),
-                       std::string(source.unsavedFileContent),
-                       std::vector<std::string>(source.commandLineArguments));
+    clangQuery.addFile(std::move(source.filePath),
+                       std::move(source.unsavedFileContent),
+                       std::move(source.commandLineArguments));
 
     clangQuery.addUnsavedFiles(unsaved);
 
diff --git a/src/tools/clangrefactoringbackend/source/clangtool.cpp b/src/tools/clangrefactoringbackend/source/clangtool.cpp
index 66f85c6d36d..5ae87793dbd 100644
--- a/src/tools/clangrefactoringbackend/source/clangtool.cpp
+++ b/src/tools/clangrefactoringbackend/source/clangtool.cpp
@@ -27,6 +27,8 @@
 
 #include <iostream>
 
+#include <nativefilepath.h>
+
 namespace ClangBackEnd {
 
 namespace {
@@ -44,67 +46,37 @@ String toNativePath(String &&path)
 }
 }
 
-void ClangTool::addFile(std::string &&directory,
-                        std::string &&fileName,
-                        std::string &&content,
-                        std::vector<std::string> &&commandLine)
+void ClangTool::addFile(FilePath &&filePath,
+                        Utils::SmallString &&content,
+                        Utils::SmallStringVector &&commandLine)
 {
-    m_fileContents.emplace_back(toNativePath(std::move(directory)),
-                                std::move(fileName),
-                                std::move(content),
-                                std::move(commandLine));
+    NativeFilePath nativeFilePath{filePath};
 
-    const auto &fileContent = m_fileContents.back();
+    m_compilationDatabase.addFile(nativeFilePath, std::move(commandLine));
+    m_sourceFilePaths.push_back(Utils::SmallStringView{nativeFilePath});
 
-    m_compilationDatabase.addFile(fileContent.directory, fileContent.fileName, fileContent.commandLine);
-    m_sourceFilePaths.push_back(fileContent.filePath);
+    m_fileContents.emplace_back(std::move(nativeFilePath), std::move(content));
 }
 
 void ClangTool::addFiles(const FilePaths &filePaths, const Utils::SmallStringVector &arguments)
 {
     for (const FilePath &filePath : filePaths) {
-        std::vector<std::string> commandLine(arguments.begin(), arguments.end());
-        commandLine.push_back(std::string(filePath.name()));
+        std::string filePathStr(filePath.path());
+        auto commandLine = arguments;
+        NativeFilePath nativeFilePath{filePath};
 
-        addFile(filePath.directory(),
-                filePath.name(),
-                {},
-                std::move(commandLine));
+        commandLine.push_back(nativeFilePath.path());
+
+        addFile(filePath.clone(), {}, std::move(commandLine));
     }
 }
 
-template <typename Container>
-void ClangTool::addFiles(const Container &filePaths,
-                         const Utils::SmallStringVector &arguments)
-{
-    for (const typename Container::value_type &filePath : filePaths) {
-        auto found = std::find(filePath.rbegin(), filePath.rend(), '/');
-
-        auto fileNameBegin = found.base();
-
-        std::vector<std::string> commandLine(arguments.begin(), arguments.end());
-        commandLine.push_back(std::string(filePath));
-
-        addFile({filePath.begin(), std::prev(fileNameBegin)},
-                {fileNameBegin, filePath.end()},
-                {},
-                std::move(commandLine));
-    }
-}
-
-template
-void ClangTool::addFiles<Utils::SmallStringVector>(const Utils::SmallStringVector &filePaths,
-                                                   const Utils::SmallStringVector &arguments);
-template
-void ClangTool::addFiles<Utils::PathStringVector>(const Utils::PathStringVector &filePaths,
-                                                  const Utils::SmallStringVector &arguments);
-
 void ClangTool::addUnsavedFiles(const V2::FileContainers &unsavedFiles)
 {
     m_unsavedFileContents.reserve(m_unsavedFileContents.size() + unsavedFiles.size());
 
-    auto convertToUnsavedFileContent = [] (const V2::FileContainer &unsavedFile) {
-        return UnsavedFileContent{toNativePath(unsavedFile.filePath.path().clone()),
+    auto convertToUnsavedFileContent = [](const V2::FileContainer &unsavedFile) {
+        return UnsavedFileContent{NativeFilePath{unsavedFile.filePath},
                                   unsavedFile.unsavedFileContent.clone()};
     };
 
@@ -120,7 +92,12 @@ llvm::StringRef toStringRef(const String &string)
 {
     return llvm::StringRef(string.data(), string.size());
 }
+
+llvm::StringRef toStringRef(const NativeFilePath &path)
+{
+    return llvm::StringRef(path.path().data(), path.path().size());
 }
+} // namespace
 
 clang::tooling::ClangTool ClangTool::createTool() const
 {
@@ -128,7 +105,7 @@ clang::tooling::ClangTool ClangTool::createTool() const
 
     for (const auto &fileContent : m_fileContents) {
         if (!fileContent.content.empty())
-            tool.mapVirtualFile(fileContent.filePath, fileContent.content);
+            tool.mapVirtualFile(toStringRef(fileContent.filePath), fileContent.content);
     }
 
     for (const auto &unsavedFileContent : m_unsavedFileContents)
diff --git a/src/tools/clangrefactoringbackend/source/clangtool.h b/src/tools/clangrefactoringbackend/source/clangtool.h
index 8b4e47df682..e3ff8357998 100644
--- a/src/tools/clangrefactoringbackend/source/clangtool.h
+++ b/src/tools/clangrefactoringbackend/source/clangtool.h
@@ -30,6 +30,7 @@
 #include <clangrefactoringbackend_global.h>
 
 #include <filecontainerv2.h>
+#include <nativefilepath.h>
 #include <sourcelocationscontainer.h>
 
 #include <clang/Tooling/Refactoring.h>
@@ -43,50 +44,34 @@ namespace ClangBackEnd {
 
 struct FileContent
 {
-    FileContent(const std::string &directory,
-                const std::string &fileName,
-                const std::string &content,
-                const std::vector<std::string> &commandLine)
-        : directory(directory),
-          fileName(fileName),
-          filePath(directory + nativeSeparator + fileName),
-          content(content),
-          commandLine(commandLine)
+    FileContent(NativeFilePath &&filePath, const Utils::SmallString &content)
+        : filePath(std::move(filePath))
+        , content(std::move(content))
     {}
 
-    std::string directory;
-    std::string fileName;
-    std::string filePath;
+    NativeFilePath filePath;
     std::string content;
-    std::vector<std::string> commandLine;
 };
 
 struct UnsavedFileContent
 {
-    UnsavedFileContent(Utils::PathString &&filePath,
-                       Utils::SmallString &&content)
-        : filePath(std::move(filePath)),
-          content(std::move(content))
+    UnsavedFileContent(NativeFilePath &&filePath, Utils::SmallString &&content)
+        : filePath(std::move(filePath))
+        , content(std::move(content))
     {}
 
-    Utils::PathString filePath;
+    NativeFilePath filePath;
     Utils::SmallString content;
 };
 
 class ClangTool
 {
 public:
-    void addFile(std::string &&directory,
-                 std::string &&fileName,
-                 std::string &&content,
-                 std::vector<std::string> &&commandLine);
-
-    template <typename Container>
-    void addFiles(const Container &filePaths,
-                  const Utils::SmallStringVector &arguments);
-    void addFiles(const FilePaths &filePaths,
-                  const Utils::SmallStringVector &arguments);
+    void addFile(FilePath &&filePath,
+                 Utils::SmallString &&content,
+                 Utils::SmallStringVector &&commandLine);
 
+    void addFiles(const FilePaths &filePaths, const Utils::SmallStringVector &arguments);
 
     void addUnsavedFiles(const V2::FileContainers &unsavedFiles);
 
@@ -102,11 +87,4 @@ private:
     std::vector<UnsavedFileContent> m_unsavedFileContents;
 };
 
-extern template
-void ClangTool::addFiles<Utils::SmallStringVector>(const Utils::SmallStringVector &filePaths,
-                                                   const Utils::SmallStringVector &arguments);
-extern template
-void ClangTool::addFiles<Utils::PathStringVector>(const Utils::PathStringVector &filePaths,
-                                                  const Utils::SmallStringVector &arguments);
-
 } // namespace ClangBackEnd
diff --git a/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.cpp b/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.cpp
index c5906aaae47..1e1609d1a4f 100644
--- a/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.cpp
+++ b/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.cpp
@@ -27,20 +27,15 @@
 
 #include "clangrefactoringbackend_global.h"
 
+#include <filepath.h>
+#include <nativefilepath.h>
+
 namespace ClangBackEnd {
 
 RefactoringCompilationDatabase::RefactoringCompilationDatabase()
 {
 }
 
-namespace {
-
-std::string concatFilePath(const clang::tooling::CompileCommand &compileCommand)
-{
-    return compileCommand.Directory + nativeSeparator + compileCommand.Filename;
-}
-}
-
 std::vector<clang::tooling::CompileCommand>
 RefactoringCompilationDatabase::getCompileCommands(llvm::StringRef filePath) const
 {
@@ -50,7 +45,7 @@ RefactoringCompilationDatabase::getCompileCommands(llvm::StringRef filePath) con
                  m_compileCommands.end(),
                  std::back_inserter(foundCommands),
                  [&] (const clang::tooling::CompileCommand &compileCommand) {
-        return filePath == concatFilePath(compileCommand);
+        return filePath == compileCommand.Filename;
     });
 
     return foundCommands;
@@ -66,7 +61,7 @@ RefactoringCompilationDatabase::getAllFiles() const
                    m_compileCommands.end(),
                    std::back_inserter(filePaths),
                    [&] (const clang::tooling::CompileCommand &compileCommand) {
-          return concatFilePath(compileCommand);
+          return compileCommand.Filename;
       });
 
     return filePaths;
@@ -78,12 +73,13 @@ RefactoringCompilationDatabase::getAllCompileCommands() const
     return m_compileCommands;
 }
 
-void RefactoringCompilationDatabase::addFile(const std::string &directory,
-                                             const std::string &fileName,
-                                             const std::vector<std::string> &commandLine)
+void RefactoringCompilationDatabase::addFile(NativeFilePathView filePath,
+                                             Utils::SmallStringVector &&commandLine)
 {
-
-    m_compileCommands.emplace_back(directory, fileName, commandLine, llvm::StringRef());
+    m_compileCommands.emplace_back(std::string(filePath.directory()),
+                                   std::string(filePath),
+                                   std::vector<std::string>(commandLine),
+                                   llvm::StringRef());
 }
 
 } // namespace ClangBackEnd
diff --git a/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.h b/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.h
index ca2d1338191..b25e43e4834 100644
--- a/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.h
+++ b/src/tools/clangrefactoringbackend/source/refactoringcompilationdatabase.h
@@ -27,6 +27,8 @@
 
 #include "clang/Tooling/CompilationDatabase.h"
 
+#include <nativefilepath.h>
+
 namespace ClangBackEnd {
 
 
@@ -39,9 +41,7 @@ public:
     std::vector<std::string> getAllFiles() const override;
     std::vector<clang::tooling::CompileCommand> getAllCompileCommands() const override;
 
-    void addFile(const std::string &directory,
-                 const std::string &fileName,
-                 const std::vector<std::string> &commandLine);
+    void addFile(NativeFilePathView filePath, Utils::SmallStringVector &&commandLine);
 
 private:
     std::vector<clang::tooling::CompileCommand> m_compileCommands;
diff --git a/src/tools/clangrefactoringbackend/source/refactoringserver.cpp b/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
index 4b51ee0d69d..83aa5a31fd8 100644
--- a/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
+++ b/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
@@ -62,10 +62,9 @@ void RefactoringServer::requestSourceLocationsForRenamingMessage(RequestSourceLo
 {
     SymbolFinder symbolFinder(message.line, message.column, m_filePathCache);
 
-    symbolFinder.addFile(std::string(message.filePath.directory()),
-                         std::string(message.filePath.name()),
-                         std::string(message.unsavedContent),
-                         std::vector<std::string>(message.commandLine));
+    symbolFinder.addFile(std::move(message.filePath),
+                         std::move(message.unsavedContent),
+                         std::move(message.commandLine));
 
     symbolFinder.findSymbol();
 
@@ -79,10 +78,9 @@ void RefactoringServer::requestSourceRangesAndDiagnosticsForQueryMessage(
 {
     ClangQuery clangQuery(m_filePathCache, message.takeQuery());
 
-    clangQuery.addFile(std::string(message.source.filePath.directory()),
-                       std::string(message.source.filePath.name()),
-                       std::string(message.source.unsavedFileContent),
-                       std::vector<std::string>(message.source.commandLineArguments));
+    clangQuery.addFile(std::move(message.source.filePath),
+                       std::move(message.source.unsavedFileContent),
+                       std::move(message.source.commandLineArguments));
 
     clangQuery.findLocations();
 
diff --git a/tests/unit/unittest/clangquery-test.cpp b/tests/unit/unittest/clangquery-test.cpp
index 8c486a47d78..35842e01439 100644
--- a/tests/unit/unittest/clangquery-test.cpp
+++ b/tests/unit/unittest/clangquery-test.cpp
@@ -94,7 +94,9 @@ TEST_F(ClangQuerySlowTest, RootSourceRangeForSimpleFunctionDeclarationRange)
 TEST_F(ClangQuerySlowTest, SourceRangeInUnsavedFileDeclarationRange)
 {
     ::ClangQuery query(filePathCache);
-    query.addFile(TESTDATA_DIR, "query_simplefunction.cpp", "#include \"unsaved.h\"", {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction.cpp"), "-std=c++14"});
+    query.addFile({TESTDATA_DIR "/query_simplefunction.cpp"},
+                  "#include \"unsaved.h\"",
+                  {"cc", toNativePath(TESTDATA_DIR "/query_simplefunction.cpp").path(), "-std=c++14"});
     query.setQuery("functionDecl()");
     ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR, "unsaved.h"}, "void unsaved();", {}};
     query.addUnsavedFiles({unsavedFile});
@@ -108,7 +110,9 @@ TEST_F(ClangQuerySlowTest, SourceRangeInUnsavedFileDeclarationRange)
 TEST_F(ClangQuerySlowTest, FileIsNotExistingButTheUnsavedDataIsParsed)
 {
     ::ClangQuery query(filePathCache);
-    query.addFile(TESTDATA_DIR, "foo.cpp", "void f() {}", {"cc", toNativePath(TESTDATA_DIR"/foo.cpp"), "-std=c++14"});
+    query.addFile({TESTDATA_DIR "/foo.cpp"},
+                  "void f() {}",
+                  {"cc", toNativePath(TESTDATA_DIR "/foo.cpp").path(), "-std=c++14"});
     query.setQuery("functionDecl()");
 
     query.findLocations();
@@ -120,9 +124,13 @@ TEST_F(ClangQuerySlowTest, FileIsNotExistingButTheUnsavedDataIsParsed)
 TEST_F(ClangQuerySlowTest, DISABLED_SourceRangeInUnsavedFileDeclarationRangeOverride) // seems not to work in Clang
 {
     ::ClangQuery query(filePathCache);
-    query.addFile(TESTDATA_DIR, "query_simplefunction.cpp", "void f() {}", {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction.cpp"), "-std=c++14"});
+    query.addFile({TESTDATA_DIR "/query_simplefunction.cpp"},
+                  "void f() {}",
+                  {"cc", toNativePath(TESTDATA_DIR "/query_simplefunction.cpp").path(), "-std=c++14"});
     query.setQuery("functionDecl()");
-    ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR, "query_simplefunction.cpp"}, "void unsaved();", {}};
+    ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR "/query_simplefunction.cpp"},
+                                                "void unsaved();",
+                                                {}};
     query.addUnsavedFiles({unsavedFile});
 
     query.findLocations();
@@ -215,8 +223,15 @@ TEST_F(ClangQuerySlowTest, DiagnosticForWrongArgumenType)
 
 void ClangQuery::SetUp()
 {
-    simpleFunctionQuery.addFile(TESTDATA_DIR, "query_simplefunction.cpp", "", {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction.cpp"), "-std=c++14"});
-    simpleClassQuery.addFile(TESTDATA_DIR, "query_simpleclass.cpp", "", {"cc", "query_simpleclass.cpp", "-std=c++14"});
-
-}
+    simpleFunctionQuery.addFile({TESTDATA_DIR "/query_simplefunction.cpp"},
+                                "",
+                                {"cc",
+                                 toNativePath(TESTDATA_DIR "/query_simplefunction.cpp").path(),
+                                 "-std=c++14"});
+    simpleClassQuery.addFile({TESTDATA_DIR "/query_simpleclass.cpp"},
+                             "",
+                             {"cc",
+                              toNativePath(TESTDATA_DIR "/query_simpleclass.cpp").path(),
+                              "-std=c++14"});
 }
+} // namespace
diff --git a/tests/unit/unittest/clangquerygatherer-test.cpp b/tests/unit/unittest/clangquerygatherer-test.cpp
index 9c575f6a0f5..b0ea9cb3e0e 100644
--- a/tests/unit/unittest/clangquerygatherer-test.cpp
+++ b/tests/unit/unittest/clangquerygatherer-test.cpp
@@ -87,13 +87,22 @@ protected:
     Utils::SmallString sourceContent{"#include \"query_simplefunction.h\"\nvoid f() {}"};
     FileContainer source{{TESTDATA_DIR, "query_simplefunction.cpp"},
                          sourceContent.clone(),
-                         {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction.cpp"), "-I", TESTDATA_DIR}};
+                         {"cc",
+                          toNativePath(TESTDATA_DIR "/query_simplefunction.cpp").path(),
+                          "-I",
+                          TESTDATA_DIR}};
     FileContainer source2{{TESTDATA_DIR, "query_simplefunction2.cpp"},
                           {},
-                          {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction2.cpp"), "-I", TESTDATA_DIR}};
+                          {"cc",
+                           toNativePath(TESTDATA_DIR "/query_simplefunction2.cpp").path(),
+                           "-I",
+                           TESTDATA_DIR}};
     FileContainer source3{{TESTDATA_DIR, "query_simplefunction3.cpp"},
                           {},
-                          {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction3.cpp"), "-I", TESTDATA_DIR}};
+                          {"cc",
+                           toNativePath(TESTDATA_DIR "/query_simplefunction3.cpp").path(),
+                           "-I",
+                           TESTDATA_DIR}};
     Utils::SmallString unsavedContent{"void f();"};
     FileContainer unsaved{{TESTDATA_DIR, "query_simplefunction.h"},
                           unsavedContent.clone(),
diff --git a/tests/unit/unittest/commandlinebuilder-test.cpp b/tests/unit/unittest/commandlinebuilder-test.cpp
index c3dad70de3c..9de48fe0d55 100644
--- a/tests/unit/unittest/commandlinebuilder-test.cpp
+++ b/tests/unit/unittest/commandlinebuilder-test.cpp
@@ -25,6 +25,8 @@
 
 #include "googletest.h"
 
+#include "filesystem-utilities.h"
+
 #include <commandlinebuilder.h>
 #include <pchtask.h>
 #include <projectpartcontainer.h>
@@ -136,7 +138,7 @@ TYPED_TEST(CommandLineBuilder, CTask)
 
     ASSERT_THAT(
         builder.commandLine,
-        ElementsAre("clang", "-x", "c-header", "-std=c11", "-nostdinc", "-nostdinc++", "/source/file.c"));
+        ElementsAre("clang", "-x", "c-header", "-std=c11", "-nostdinc", "-nostdinc++", toNativePath("/source/file.c").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, ObjectiveCTask)
@@ -154,7 +156,7 @@ TYPED_TEST(CommandLineBuilder, ObjectiveCTask)
                             "-std=c11",
                             "-nostdinc",
                             "-nostdinc++",
-                            "/source/file.c"));
+                            toNativePath("/source/file.c").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, CppTask)
@@ -171,7 +173,7 @@ TYPED_TEST(CommandLineBuilder, CppTask)
                             "-std=c++98",
                             "-nostdinc",
                             "-nostdinc++",
-                            "/source/file.cpp"));
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, ObjectiveCppTask)
@@ -189,7 +191,7 @@ TYPED_TEST(CommandLineBuilder, ObjectiveCppTask)
                             "-std=c++98",
                             "-nostdinc",
                             "-nostdinc++",
-                            "/source/file.cpp"));
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, Cpp98)
@@ -422,18 +424,18 @@ TYPED_TEST(CommandLineBuilder, IncludesOrder)
                             "-nostdinc",
                             "-nostdinc++",
                             "-I",
-                            "/include/foo",
+                            toNativePath("/include/foo").path(),
                             "-I",
-                            "/include/bar",
+                            toNativePath("/include/bar").path(),
                             "-F",
-                            "/system/foo",
+                            toNativePath("/system/foo").path(),
                             "-isystem",
-                            "/system/bar",
+                            toNativePath("/system/bar").path(),
                             "-isystem",
-                            "/builtin/foo",
+                            toNativePath("/builtin/foo").path(),
                             "-isystem",
-                            "/builtin/bar",
-                            "/source/file.cpp"));
+                            toNativePath("/builtin/bar").path(),
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, EmptySourceFile)
@@ -455,7 +457,7 @@ TYPED_TEST(CommandLineBuilder, SourceFile)
                             "-std=c++98",
                             "-nostdinc",
                             "-nostdinc++",
-                            "/source/file.cpp"));
+                            toNativePath("/source/file.cpp").path()));
 }
 
 
@@ -470,7 +472,7 @@ TYPED_TEST(CommandLineBuilder, EmptyOutputFile)
                             "-std=c++98",
                             "-nostdinc",
                             "-nostdinc++",
-                            "/source/file.cpp"));
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, OutputFile)
@@ -485,8 +487,8 @@ TYPED_TEST(CommandLineBuilder, OutputFile)
                             "-nostdinc",
                             "-nostdinc++",
                             "-o",
-                            "/output/file.o",
-                            "/source/file.cpp"));
+                            toNativePath("/output/file.o").path(),
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, IncludePchPath)
@@ -503,10 +505,10 @@ TYPED_TEST(CommandLineBuilder, IncludePchPath)
                             "-Xclang",
                             "-include-pch",
                             "-Xclang",
-                            "/pch/file.pch",
+                            toNativePath("/pch/file.pch").path(),
                             "-o",
-                            "/output/file.o",
-                            "/source/file.cpp"));
+                            toNativePath("/output/file.o").path(),
+                            toNativePath("/source/file.cpp").path()));
 }
 
 TYPED_TEST(CommandLineBuilder, CompilerMacros)
diff --git a/tests/unit/unittest/filesystem-utilities.h b/tests/unit/unittest/filesystem-utilities.h
index 3bbafdf3686..9a4fd8e2db7 100644
--- a/tests/unit/unittest/filesystem-utilities.h
+++ b/tests/unit/unittest/filesystem-utilities.h
@@ -26,32 +26,27 @@
 #pragma once
 
 #include <utils/hostosinfo.h>
-#include <utils/smallstring.h>
 
-#include <string>
+#include <nativefilepath.h>
 
-// use std::filesystem::path if it is supported by all compilers
-static const char nativeSeparator = Utils::HostOsInfo::isWindowsHost() ? '\\' : '/';
-
-
-template <std::size_t Size>
-std::string toNativePath(const char (&text)[Size])
+template<std::size_t Size>
+ClangBackEnd::NativeFilePath toNativePath(const char (&text)[Size])
 {
-    std::string path = text;
+    ClangBackEnd::FilePath path = text;
 
-    if (Utils::HostOsInfo::isWindowsHost())
-        std::replace(path.begin(), path.end(), '/', '\\');
-
-    return path;
+    return ClangBackEnd::NativeFilePath{path};
 }
 
-inline
-std::string toNativePath(const QString &qStringPath)
+inline ClangBackEnd::NativeFilePath toNativePath(const QString &text)
 {
-    auto path = qStringPath.toStdString();
+    ClangBackEnd::FilePath path{text};
 
-    if (Utils::HostOsInfo::isWindowsHost())
-        std::replace(path.begin(), path.end(), '/', '\\');
-
-    return path;
+    return ClangBackEnd::NativeFilePath{path};
+}
+
+inline ClangBackEnd::NativeFilePath toNativePath(Utils::SmallStringView text)
+{
+    ClangBackEnd::FilePath path{text};
+
+    return ClangBackEnd::NativeFilePath{path};
 }
diff --git a/tests/unit/unittest/gtest-creator-printing.cpp b/tests/unit/unittest/gtest-creator-printing.cpp
index 3901cb0d305..30660376e1f 100644
--- a/tests/unit/unittest/gtest-creator-printing.cpp
+++ b/tests/unit/unittest/gtest-creator-printing.cpp
@@ -69,10 +69,24 @@
 #include <coreplugin/find/searchresultitem.h>
 #include <coreplugin/locator/ilocatorfilter.h>
 
+#include <clang/Tooling/CompilationDatabase.h>
+
 namespace {
 ClangBackEnd::FilePathCaching *filePathCache = nullptr;
 }
 
+namespace clang {
+namespace tooling {
+struct CompileCommand;
+
+std::ostream &operator<<(std::ostream &out, const CompileCommand &command)
+{
+    return out << "(" << command.Directory << ", " << command.Filename << ", "
+               << command.CommandLine << ", " << command.Output << ")";
+}
+} // namespace tooling
+} // namespace clang
+
 void PrintTo(const Utf8String &text, ::std::ostream *os)
 {
     *os << text;
diff --git a/tests/unit/unittest/gtest-creator-printing.h b/tests/unit/unittest/gtest-creator-printing.h
index ec54af30850..d0f0013f609 100644
--- a/tests/unit/unittest/gtest-creator-printing.h
+++ b/tests/unit/unittest/gtest-creator-printing.h
@@ -40,6 +40,14 @@
 class Utf8String;
 void PrintTo(const Utf8String &text, ::std::ostream *os);
 
+namespace clang {
+namespace tooling {
+struct CompileCommand;
+
+std::ostream &operator<<(std::ostream &out, const CompileCommand &command);
+} // namespace tooling
+} // namespace clang
+
 namespace Core {
 class LocatorFilterEntry;
 
diff --git a/tests/unit/unittest/nativefilepath-test.cpp b/tests/unit/unittest/nativefilepath-test.cpp
index 864c91dc608..327cff42dc6 100644
--- a/tests/unit/unittest/nativefilepath-test.cpp
+++ b/tests/unit/unittest/nativefilepath-test.cpp
@@ -25,6 +25,7 @@
 
 #include "googletest.h"
 
+#include <filepath.h>
 #include <nativefilepath.h>
 
 namespace {
diff --git a/tests/unit/unittest/pchcreator-test.cpp b/tests/unit/unittest/pchcreator-test.cpp
index a75ff4267ab..8a1e1ffa8ef 100644
--- a/tests/unit/unittest/pchcreator-test.cpp
+++ b/tests/unit/unittest/pchcreator-test.cpp
@@ -26,6 +26,7 @@
 #include "googletest.h"
 
 #include "fakeprocess.h"
+#include "filesystem-utilities.h"
 
 #include "mockclangpathwatcher.h"
 #include "mockpchmanagerclient.h"
@@ -144,11 +145,11 @@ TEST_F(PchCreator, CreateProjectPartClangCompilerArguments)
                             "-nostdinc",
                             "-nostdinc++",
                             "-I",
-                            TESTDATA_DIR "/builddependencycollector/project",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/project").path(),
                             "-isystem",
-                            TESTDATA_DIR "/builddependencycollector/external",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/external").path(),
                             "-isystem",
-                            TESTDATA_DIR "/builddependencycollector/system",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/system").path(),
                             "-o",
                             "project.pch",
                             "project.h"));
@@ -170,11 +171,11 @@ TEST_F(PchCreator, CreateProjectPartClangCompilerArgumentsWithSystemPch)
                             "-nostdinc",
                             "-nostdinc++",
                             "-I",
-                            TESTDATA_DIR "/builddependencycollector/project",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/project").path(),
                             "-isystem",
-                            TESTDATA_DIR "/builddependencycollector/external",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/external").path(),
                             "-isystem",
-                            TESTDATA_DIR "/builddependencycollector/system",
+                            toNativePath(TESTDATA_DIR "/builddependencycollector/system").path(),
                             "-Xclang",
                             "-include-pch",
                             "-Xclang",
diff --git a/tests/unit/unittest/refactoringcompilationdatabase-test.cpp b/tests/unit/unittest/refactoringcompilationdatabase-test.cpp
index b635d174a98..59f88f8b53d 100644
--- a/tests/unit/unittest/refactoringcompilationdatabase-test.cpp
+++ b/tests/unit/unittest/refactoringcompilationdatabase-test.cpp
@@ -24,8 +24,10 @@
 ****************************************************************************/
 
 #include "googletest.h"
+#include "filesystem-utilities.h"
 
 #include <refactoringcompilationdatabase.h>
+#include <nativefilepath.h>
 
 #include <utils/smallstring.h>
 
@@ -38,16 +40,16 @@ using testing::PrintToString;
 
 namespace {
 
-MATCHER_P3(IsCompileCommand, directory, fileName, commandLine,
-           std::string(negation ? "isn't" : "is")
-           + " compile command with directory "+ PrintToString(directory)
-           + ", file name " + PrintToString(fileName)
-           + " and command line " + PrintToString(commandLine)
-           )
+MATCHER_P3(IsCompileCommand,
+           directory,
+           filePath,
+           commandLine,
+           std::string(negation ? "isn't" : "is") + " compile command with directory "
+               + PrintToString(directory) + ", file name " + PrintToString(filePath)
+               + " and command line " + PrintToString(commandLine))
 {
-    if (arg.Directory != directory
-            || arg.Filename != fileName
-            || arg.CommandLine != commandLine)
+    if (arg.Directory != std::string(directory) || arg.Filename != std::string(filePath)
+        || arg.CommandLine != commandLine)
         return false;
 
     return true;
@@ -56,7 +58,11 @@ MATCHER_P3(IsCompileCommand, directory, fileName, commandLine,
 class RefactoringCompilationDatabase : public ::testing::Test
 {
 protected:
-    void SetUp();
+    RefactoringCompilationDatabase()
+    {
+        database.addFile(ClangBackEnd::NativeFilePathView{temporarySourceFilePath},
+                         {"cc", toNativePath(temporaryDirectoryPath + "/data.cpp").path(), "-DNO_DEBUG"});
+    }
 
 protected:
     ClangBackEnd::RefactoringCompilationDatabase database;
@@ -76,18 +82,28 @@ TEST_F(RefactoringCompilationDatabase, CompileCommandForFilePath)
 {
     auto compileCommands = database.getAllCompileCommands();
 
-    ASSERT_THAT(compileCommands, Contains(IsCompileCommand(temporaryDirectoryPath,
-                                                           "data.cpp",
-                                                           std::vector<std::string>{"cc", "data.cpp", "-DNO_DEBUG"})));
+    ASSERT_THAT(compileCommands,
+                Contains(IsCompileCommand(
+                    temporaryDirectoryPath,
+                    toNativePath(temporaryDirectoryPath + "/data.cpp").path(),
+                    std::vector<std::string>{
+                        "cc",
+                        std::string(toNativePath(temporaryDirectoryPath + "/data.cpp").path()),
+                        "-DNO_DEBUG"})));
 }
 
 TEST_F(RefactoringCompilationDatabase, NoCompileCommandForFilePath)
 {
     auto compileCommands = database.getAllCompileCommands();
 
-    ASSERT_THAT(compileCommands, Not(Contains(IsCompileCommand(temporaryDirectoryPath,
-                                                               "data.cpp2",
-                                                               std::vector<std::string>{"cc", "data.cpp", "-DNO_DEBUG"}))));
+    ASSERT_THAT(compileCommands,
+                Not(Contains(IsCompileCommand(
+                    temporaryDirectoryPath,
+                    toNativePath(temporaryDirectoryPath + "/data.cpp2").path(),
+                    std::vector<std::string>{
+                        "cc",
+                        std::string(toNativePath(temporaryDirectoryPath + "/data.cpp").path()),
+                        "-DNO_DEBUG"}))));
 }
 
 TEST_F(RefactoringCompilationDatabase, FilePaths)
@@ -96,10 +112,4 @@ TEST_F(RefactoringCompilationDatabase, FilePaths)
 
     ASSERT_THAT(filePaths, Contains(std::string(temporarySourceFilePath)));
 }
-
-void RefactoringCompilationDatabase::SetUp()
-{
-    database.addFile(std::string(temporaryDirectoryPath), "data.cpp", {"cc", "data.cpp", "-DNO_DEBUG"});
-}
-
-}
+} // namespace
diff --git a/tests/unit/unittest/refactoringserver-test.cpp b/tests/unit/unittest/refactoringserver-test.cpp
index b8b97437e4a..56f5e6950dd 100644
--- a/tests/unit/unittest/refactoringserver-test.cpp
+++ b/tests/unit/unittest/refactoringserver-test.cpp
@@ -102,8 +102,9 @@ protected:
     Utils::SmallString sourceContent{"void f()\n {}"};
     FileContainer source{{TESTDATA_DIR, "query_simplefunction.cpp"},
                          sourceContent.clone(),
-                         {"cc", toNativePath(TESTDATA_DIR"/query_simplefunction.cpp")}};
-    QTemporaryFile temporaryFile{Utils::TemporaryDirectory::masterDirectoryPath() + "/clangQuery-XXXXXX.cpp"};
+                         {"cc", toNativePath(TESTDATA_DIR "/query_simplefunction.cpp").path()}};
+    QTemporaryFile temporaryFile{Utils::TemporaryDirectory::masterDirectoryPath()
+                                 + "/clangQuery-XXXXXX.cpp"};
     int processingSlotCount = 2;
 };
 
@@ -266,10 +267,11 @@ TEST_F(RefactoringServer, PollTimerNotIsActiveAfterCanceling)
 
 TEST_F(RefactoringServerSlowTest, ForValidRequestSourceRangesAndDiagnosticsGetSourceRange)
 {
-    RequestSourceRangesAndDiagnosticsForQueryMessage message("functionDecl()",
-                                                             {FilePath(temporaryFile.fileName()),
-                                                              "void f() {}",
-                                                              {"cc", toNativePath(temporaryFile.fileName())}});
+    RequestSourceRangesAndDiagnosticsForQueryMessage message(
+        "functionDecl()",
+        {FilePath(temporaryFile.fileName()),
+         "void f() {}",
+         {"cc", toNativePath(temporaryFile.fileName()).path()}});
 
     EXPECT_CALL(mockRefactoringClient,
                 sourceRangesAndDiagnosticsForQueryMessage(
@@ -285,10 +287,11 @@ TEST_F(RefactoringServerSlowTest, ForValidRequestSourceRangesAndDiagnosticsGetSo
 
 TEST_F(RefactoringServerSlowTest, ForInvalidRequestSourceRangesAndDiagnosticsGetDiagnostics)
 {
-    RequestSourceRangesAndDiagnosticsForQueryMessage message("func()",
-                                                             {FilePath(temporaryFile.fileName()),
-                                                              "void f() {}",
-                                                              {"cc", toNativePath(temporaryFile.fileName())}});
+    RequestSourceRangesAndDiagnosticsForQueryMessage message(
+        "func()",
+        {FilePath(temporaryFile.fileName()),
+         "void f() {}",
+         {"cc", toNativePath(temporaryFile.fileName()).path()}});
 
     EXPECT_CALL(mockRefactoringClient,
                 sourceRangesAndDiagnosticsForQueryMessage(
diff --git a/tests/unit/unittest/sourcerangeextractor-test.cpp b/tests/unit/unittest/sourcerangeextractor-test.cpp
index ae9d670bf4b..171db9b956d 100644
--- a/tests/unit/unittest/sourcerangeextractor-test.cpp
+++ b/tests/unit/unittest/sourcerangeextractor-test.cpp
@@ -57,7 +57,9 @@ protected:
     void TearDown() override;
 
 protected:
-    TestClangTool clangTool{TESTDATA_DIR, "sourcerangeextractor_location.cpp", "",  {"cc", "sourcerangeextractor_location.cpp"}};
+    TestClangTool clangTool{{TESTDATA_DIR "/sourcerangeextractor_location.cpp"},
+                            "",
+                            {"cc", "sourcerangeextractor_location.cpp"}};
     ClangBackEnd::SourceRangesContainer sourceRangesContainer;
     const clang::SourceManager &sourceManager{clangTool.sourceManager()};
     Sqlite::Database database{":memory:", Sqlite::JournalMode::Memory};
diff --git a/tests/unit/unittest/symbolfinder-test.cpp b/tests/unit/unittest/symbolfinder-test.cpp
index 6ab0bd06cd9..1dad3184d68 100644
--- a/tests/unit/unittest/symbolfinder-test.cpp
+++ b/tests/unit/unittest/symbolfinder-test.cpp
@@ -31,28 +31,30 @@
 
 #include "filesystem-utilities.h"
 
-using ClangBackEnd::SymbolFinder;
 using ClangBackEnd::FileContent;
-
+using ClangBackEnd::FilePathView;
+using ClangBackEnd::NativeFilePath;
+using ClangBackEnd::NativeFilePathView;
+using ClangBackEnd::SymbolFinder;
 namespace {
 
-MATCHER_P2(IsSourceLocation, line, column,
-           std::string(negation ? "isn't" : "is")
-           + "line " + PrintToString(line)
-           + ", column " + PrintToString(column)
-           )
+inline bool operator==(const ClangBackEnd::NativeFilePath &first, const std::string &second)
+{
+    return first.path() == second;
+}
+MATCHER_P2(IsSourceLocation,
+           line,
+           column,
+           std::string(negation ? "isn't" : "is") + "line " + PrintToString(line) + ", column "
+               + PrintToString(column))
 {
     return arg.line == uint(line) && arg.column == uint(column);
 }
 
-MATCHER_P(StrEq, text,
-           std::string(negation ? "isn't" : "is")
-           + " text " + PrintToString(text)
-           )
+MATCHER_P(StrEq, text, std::string(negation ? "isn't" : "is") + " text " + PrintToString(text))
 {
     return std::string(arg.data(), arg.size()) == std::string(text);
 }
-
 using Finder = SymbolFinder;
 
 class SymbolFinder : public testing::Test
@@ -65,7 +67,7 @@ using SymbolFinderSlowTest = SymbolFinder;
 
 TEST_F(SymbolFinder, FileContentFilePath)
 {
-    FileContent fileContent(toNativePath("/tmp"), "data.cpp", "int variable;", {"cc", "data.cpp"});
+    FileContent fileContent(NativeFilePath{FilePathView{"/tmp/data.cpp"}}, "int variable;");
 
     ASSERT_THAT(fileContent.filePath, toNativePath("/tmp/data.cpp"));
 }
@@ -73,7 +75,9 @@ TEST_F(SymbolFinder, FileContentFilePath)
 TEST_F(SymbolFinderSlowTest, FindName)
 {
     Finder finder(1, 5, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "int variable;", {"cc", "renamevariable.cpp"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "int variable;",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path()});
 
     finder.findSymbol();
 
@@ -83,7 +87,9 @@ TEST_F(SymbolFinderSlowTest, FindName)
 TEST_F(SymbolFinderSlowTest, FindNameInUnsavedFile)
 {
     Finder finder(1, 5, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "int newVariable;", {"cc", "renamevariable.cpp"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "int newVariable;",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path()});
 
     finder.findSymbol();
 
@@ -93,7 +99,9 @@ TEST_F(SymbolFinderSlowTest, FindNameInUnsavedFile)
 TEST_F(SymbolFinderSlowTest, FindUsrs)
 {
     Finder finder(1, 5, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "int variable;", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "int variable;",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -103,7 +111,9 @@ TEST_F(SymbolFinderSlowTest, FindUsrs)
 TEST_F(SymbolFinderSlowTest, VariableDeclarationSourceLocations)
 {
     Finder finder(1, 5, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -115,7 +125,9 @@ TEST_F(SymbolFinderSlowTest, VariableDeclarationSourceLocations)
 TEST_F(SymbolFinderSlowTest, VariableUsageSourceLocations)
 {
     Finder finder(3, 9, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -127,7 +139,9 @@ TEST_F(SymbolFinderSlowTest, VariableUsageSourceLocations)
 TEST_F(SymbolFinderSlowTest, TemplateMemberVariableDeclarationSourceLocations)
 {
     Finder finder(8, 18, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -140,7 +154,9 @@ TEST_F(SymbolFinderSlowTest, TemplateMemberVariableDeclarationSourceLocations)
 TEST_F(SymbolFinderSlowTest, TemplateMemberVariableUsageSourceLocations)
 {
     Finder finder(15, 14, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -153,7 +169,9 @@ TEST_F(SymbolFinderSlowTest, TemplateMemberVariableUsageSourceLocations)
 TEST_F(SymbolFinderSlowTest, TemplateMemberVariableUsageInLambdaSourceLocations)
 {
     Finder finder(18, 19, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "renamevariable.cpp", "", {"cc", "renamevariable.cpp", "-std=c++14"});
+    finder.addFile({TESTDATA_DIR "/renamevariable.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/renamevariable.cpp").path(), "-std=c++14"});
 
     finder.findSymbol();
 
@@ -166,7 +184,9 @@ TEST_F(SymbolFinderSlowTest, TemplateMemberVariableUsageInLambdaSourceLocations)
 TEST_F(SymbolFinderSlowTest, CursorOverMacroDefintionSymbolName)
 {
     Finder finder(1, 9, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -176,7 +196,9 @@ TEST_F(SymbolFinderSlowTest, CursorOverMacroDefintionSymbolName)
 TEST_F(SymbolFinderSlowTest, CursorOverMacroExpansionSymbolName)
 {
     Finder finder(10, 10, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -186,7 +208,9 @@ TEST_F(SymbolFinderSlowTest, CursorOverMacroExpansionSymbolName)
 TEST_F(SymbolFinderSlowTest, FindMacroDefinition)
 {
     Finder finder(1, 9, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -197,7 +221,9 @@ TEST_F(SymbolFinderSlowTest, FindMacroDefinition)
 TEST_F(SymbolFinderSlowTest, FindMacroExpansion)
 {
     Finder finder(1, 9, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -208,7 +234,9 @@ TEST_F(SymbolFinderSlowTest, FindMacroExpansion)
 TEST_F(SymbolFinderSlowTest, DoNotFindUndedefinedMacroExpansion)
 {
     Finder finder(1, 9, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -219,7 +247,9 @@ TEST_F(SymbolFinderSlowTest, DoNotFindUndedefinedMacroExpansion)
 TEST_F(SymbolFinderSlowTest, FindMacroDefinitionFromMacroExpansion)
 {
     Finder finder(10, 10, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -231,7 +261,9 @@ TEST_F(SymbolFinderSlowTest, FindMacroDefinitionFromMacroExpansion)
 TEST_F(SymbolFinderSlowTest, FindMacroExpansionBeforeMacroExpansionWithCursor)
 {
     Finder finder(12, 10, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -242,7 +274,9 @@ TEST_F(SymbolFinderSlowTest, FindMacroExpansionBeforeMacroExpansionWithCursor)
 TEST_F(SymbolFinderSlowTest, FindMacroExpansionAfterMacroExpansionWithCursor)
 {
     Finder finder(10, 10, filePathCaching);
-    finder.addFile(TESTDATA_DIR, "symbolfinder_macro.cpp", "", {"cc", "symbolfinder_macro.cpp"});
+    finder.addFile({TESTDATA_DIR "/symbolfinder_macro.cpp"},
+                   "",
+                   {"cc", toNativePath(TESTDATA_DIR "/symbolfinder_macro.cpp").path()});
 
     finder.findSymbol();
 
@@ -250,4 +284,4 @@ TEST_F(SymbolFinderSlowTest, FindMacroExpansionAfterMacroExpansionWithCursor)
                 Contains(IsSourceLocation(12, 10)));
 }
 
-}
+} // namespace
diff --git a/tests/unit/unittest/symbolindexer-test.cpp b/tests/unit/unittest/symbolindexer-test.cpp
index 104c17b11b3..ce0fadfdf8c 100644
--- a/tests/unit/unittest/symbolindexer-test.cpp
+++ b/tests/unit/unittest/symbolindexer-test.cpp
@@ -24,6 +24,7 @@
 ****************************************************************************/
 
 #include "googletest.h"
+#include "filesystem-utilities.h"
 #include "mockclangpathwatcher.h"
 #include "mocksymbolscollector.h"
 #include "mocksymbolstorage.h"
@@ -273,15 +274,15 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsAddFilesInCollector)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
 
     indexer.updateProjectParts({projectPart1});
 }
@@ -303,19 +304,19 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsAddFilesWithPrecompiledHeaderInColl
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes",
+                                    toNativePath("/includes").path(),
                                     "-Xclang",
                                     "-include-pch",
                                     "-Xclang",
-                                    "/path/to/pch")));
+                                    toNativePath("/path/to/pch").path())));
 
     indexer.updateProjectParts({projectPart1});
 }
@@ -336,15 +337,15 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsAddFilesWithoutPrecompiledHeaderInC
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
 
     indexer.updateProjectParts({projectPart1});
 }
@@ -516,15 +517,15 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsInOrderWithoutProjectPartArtifact)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
     EXPECT_CALL(mockCollector, collectSymbols());
     EXPECT_CALL(mockSqliteTransactionBackend, immediateBegin());
     EXPECT_CALL(mockSymbolStorage, addSymbolsAndSourceLocations(symbolEntries, sourceLocations));
@@ -568,15 +569,15 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsInOrderWithProjectPartArtifact)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
     EXPECT_CALL(mockCollector, collectSymbols());
     EXPECT_CALL(mockSqliteTransactionBackend, immediateBegin());
     EXPECT_CALL(mockSymbolStorage, addSymbolsAndSourceLocations(symbolEntries, sourceLocations));
@@ -624,15 +625,15 @@ TEST_F(SymbolIndexer, UpdateChangedPathCallsInOrder)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
     EXPECT_CALL(mockCollector, collectSymbols());
     EXPECT_CALL(mockSqliteTransactionBackend, immediateBegin());
     EXPECT_CALL(mockSymbolStorage, addSymbolsAndSourceLocations(symbolEntries, sourceLocations));
@@ -686,19 +687,19 @@ TEST_F(SymbolIndexer, UpdateChangedPathIsUsingPrecompiledHeader)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes",
+                                    toNativePath("/includes").path(),
                                     "-Xclang",
                                     "-include-pch",
                                     "-Xclang",
-                                    "/path/to/pch")));
+                                    toNativePath("/path/to/pch").path())));
 
     indexer.pathsChanged({sourceFileIds[0]});
 }
@@ -721,15 +722,15 @@ TEST_F(SymbolIndexer, UpdateChangedPathIsNotUsingPrecompiledHeaderIfItNotExists)
                                     "-DBAR=1",
                                     "-DFOO=1",
                                     "-I",
-                                    "/project/includes",
+                                    toNativePath("/project/includes").path(),
                                     "-I",
-                                    "/other/project/includes",
+                                    toNativePath("/other/project/includes").path(),
                                     "-isystem",
-                                    TESTDATA_DIR,
+                                    toNativePath(TESTDATA_DIR).path(),
                                     "-isystem",
-                                    "/other/includes",
+                                    toNativePath("/other/includes").path(),
                                     "-isystem",
-                                    "/includes")));
+                                    toNativePath("/includes").path())));
 
     indexer.pathsChanged({sourceFileIds[0]});
 }
diff --git a/tests/unit/unittest/testclangtool.cpp b/tests/unit/unittest/testclangtool.cpp
index de41e42a814..bea5afeb4c8 100644
--- a/tests/unit/unittest/testclangtool.cpp
+++ b/tests/unit/unittest/testclangtool.cpp
@@ -25,12 +25,11 @@
 
 #include "testclangtool.h"
 
-TestClangTool::TestClangTool(std::string &&directory,
-                             std::string &&fileName,
-                             std::string &&content,
-                             std::vector<std::string> &&commandLine)
+TestClangTool::TestClangTool(ClangBackEnd::FilePath &&filePath,
+                             Utils::SmallString &&content,
+                             Utils::SmallStringVector &&commandLine)
 {
-    addFile(std::move(directory), std::move(fileName), std::move(content), std::move(commandLine));
+    addFile(std::move(filePath), std::move(content), std::move(commandLine));
 
     auto clangTool = createTool();
 
diff --git a/tests/unit/unittest/testclangtool.h b/tests/unit/unittest/testclangtool.h
index f8ae0caf165..448c4e51ae8 100644
--- a/tests/unit/unittest/testclangtool.h
+++ b/tests/unit/unittest/testclangtool.h
@@ -30,10 +30,9 @@
 class TestClangTool : public ClangBackEnd::ClangTool
 {
 public:
-    TestClangTool(std::string &&directory,
-                  std::string &&fileName,
-                  std::string &&content,
-                  std::vector<std::string> &&commandLine);
+    TestClangTool(ClangBackEnd::FilePath &&filePath,
+                  Utils::SmallString &&content,
+                  Utils::SmallStringVector &&commandLine);
 
     const clang::ASTUnit *ast() const;
     const clang::SourceManager &sourceManager() const;