diff --git a/Tests/FileIO/TestBoostGmlInterface.cpp b/Tests/FileIO/TestBoostGmlInterface.cpp
index c06c927e87399d90977084e1e7c7dc285c77cf56..28ef94f5ce22ab0e66853a30e0cb8f2a31dc26ed 100644
--- a/Tests/FileIO/TestBoostGmlInterface.cpp
+++ b/Tests/FileIO/TestBoostGmlInterface.cpp
@@ -26,8 +26,8 @@
 TEST_F(TestGmlInterface, BoostXmlGmlWriterReaderTest)
 {
     // Writer test
-    std::string test_data_file(
-        fs::temp_directory_path() /= BaseLib::random_string(32) + ".gml");
+    std::string test_data_file =
+        (fs::temp_directory_path() /= BaseLib::random_string(32) + ".gml").string();
 
     GeoLib::IO::BoostXmlGmlInterface xml(geo_objects);
     xml.setNameForExport(geo_name);
diff --git a/Tests/FileIO/TestCsvReader.cpp b/Tests/FileIO/TestCsvReader.cpp
index 9111a60972eb3debe184d7695f0c48cbb66e13c9..7f7bb2c720cca8c44ad867dd212006fee28cc6d7 100644
--- a/Tests/FileIO/TestCsvReader.cpp
+++ b/Tests/FileIO/TestCsvReader.cpp
@@ -25,9 +25,9 @@ class CsvInterfaceTest : public ::testing::Test
 {
 public:
     CsvInterfaceTest()
-        : _file_name(
-            fs::temp_directory_path() /= BaseLib::random_string(32) + ".csv")
     {
+        _file_name =
+            (fs::temp_directory_path() /= BaseLib::random_string(32) + ".csv").string();
         std::ofstream out(_file_name);
         out << "id\tx\ty\tz\tname\tvalue1\tvalue_two\n";
         out << "0\t642015.538\t5724666.445\t391.759\ttest_a\t11.05303121\t436.913\t133\n";
diff --git a/Tests/FileIO/TestCsvWriter.cpp b/Tests/FileIO/TestCsvWriter.cpp
index d6d6eb6d6fc30ce593141d55a655c45a171c3e13..3c5c3340e0b6103a5d4fdb635075a8efeba4f8e9 100644
--- a/Tests/FileIO/TestCsvWriter.cpp
+++ b/Tests/FileIO/TestCsvWriter.cpp
@@ -22,7 +22,7 @@
 TEST(CsvWriter, WriteReadTest)
 {
     std::string test_file(
-        fs::temp_directory_path() /= BaseLib::random_string(32));
+        (fs::temp_directory_path() /= BaseLib::random_string(32)).string());
 
     std::vector<std::string> str_vec {"Red", "Orange", "Yellow", "Green", "Blue", "Indigo", "Violet" };
     std::vector<int> int_vec { 1, 2, 4, 8, 16, 32, 64 };
diff --git a/Tests/FileIO/TestTetGenInterface.cpp b/Tests/FileIO/TestTetGenInterface.cpp
index e4c56d8f7b022becabfbe542648765d36aad3518..ae915556f966c10af0c69eebbaf063677e82938a 100644
--- a/Tests/FileIO/TestTetGenInterface.cpp
+++ b/Tests/FileIO/TestTetGenInterface.cpp
@@ -56,8 +56,8 @@ TEST(FileIO, DISABLED_TetGenSmeshInterface)
     std::unique_ptr<MeshLib::Mesh const> const mesh (MeshLib::IO::readMeshFromFile(file_name));
 
     std::string const tg_new_name (BaseLib::random_string(32));
-    std::string const output_name(
-        fs::temp_directory_path() /= tg_new_name + ".smesh");
+    std::string const output_name =
+        (fs::temp_directory_path() /= tg_new_name + ".smesh").string();
     std::cout << output_name << std::endl;
     std::vector<MeshLib::Node> attr_pnts;
     FileIO::TetGenInterface tgi;
diff --git a/Tests/FileIO_Qt/TestQtGmlInterface.cpp b/Tests/FileIO_Qt/TestQtGmlInterface.cpp
index 1f517301b5cb087e78a692e9f941b407605a30ea..2fe80964556297d040749b7baf4e5018fabe45ad 100644
--- a/Tests/FileIO_Qt/TestQtGmlInterface.cpp
+++ b/Tests/FileIO_Qt/TestQtGmlInterface.cpp
@@ -26,8 +26,8 @@
 TEST_F(TestGmlInterface, QtXmlGmlWriterReaderTest)
 {
     // Writer test
-    std::string test_data_file(
-        fs::temp_directory_path() /= BaseLib::random_string(32));
+    std::string test_data_file =
+        (fs::temp_directory_path() /= BaseLib::random_string(32)).string();
 
     GeoLib::IO::XmlGmlInterface xml(geo_objects);
     xml.setNameForExport(geo_name);
diff --git a/Tests/GeoLib/IO/TestGLIReader.cpp b/Tests/GeoLib/IO/TestGLIReader.cpp
index 834d62049cf81719eeda3a0b97a4317a1745fd28..331bc924eab41b35c062e9da87872615e2b282ee 100644
--- a/Tests/GeoLib/IO/TestGLIReader.cpp
+++ b/Tests/GeoLib/IO/TestGLIReader.cpp
@@ -51,8 +51,7 @@ protected:
 
 TEST_F(OGSIOVer4InterfaceTest, SimpleTIN)
 {
-    std::string tin_fname(_surface_fname);
-    std::ofstream tin_out (tin_fname);
+    std::ofstream tin_out (_surface_fname);
     tin_out << "0 0.0 0.0 0.0 1.0 0.0.0 0.0 0.0 1.0\n";
     tin_out << "1 0.0 0.0 0.0 1.0 0.0.0 0.0 1.0 1.0\n";
     tin_out.close();
@@ -61,7 +60,7 @@ TEST_F(OGSIOVer4InterfaceTest, SimpleTIN)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -82,7 +81,7 @@ TEST_F(OGSIOVer4InterfaceTest, StillCorrectTINWihtAdditionalValueAtEndOfLine)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -102,7 +101,7 @@ TEST_F(OGSIOVer4InterfaceTest, InvalidTIN_ZeroAreaTri)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -123,7 +122,7 @@ TEST_F(OGSIOVer4InterfaceTest, InvalidTIN_LineDoesNotStartWithID)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -143,7 +142,7 @@ TEST_F(OGSIOVer4InterfaceTest, InvalidTIN_PointIsMissing)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -162,7 +161,7 @@ TEST_F(OGSIOVer4InterfaceTest, InvalidTIN_CoordOfPointIsMissing)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
@@ -181,7 +180,7 @@ TEST_F(OGSIOVer4InterfaceTest, SimpleTIN_AdditionalEmptyLinesAtEnd)
     GeoLib::GEOObjects geometries;
     std::vector<std::string> errors;
     std::string geometry_name("TestGeometry");
-    FileIO::Legacy::readGLIFileV4(_gli_fname, geometries, geometry_name,
+    FileIO::Legacy::readGLIFileV4(_gli_fname.string(), geometries, geometry_name,
                                   errors, "dummy_for_gmsh_path");
 
     std::vector<GeoLib::Surface*> const*
diff --git a/Tests/MeshLib/TestVtkMappedMeshSource.cpp b/Tests/MeshLib/TestVtkMappedMeshSource.cpp
index 6c951246412f28f425fa9e240394fbd4ee6bfbd9..bd00c820b455259fd2f50a3dbf7d75059b9a7bd2 100644
--- a/Tests/MeshLib/TestVtkMappedMeshSource.cpp
+++ b/Tests/MeshLib/TestVtkMappedMeshSource.cpp
@@ -152,8 +152,8 @@ TEST_F(InSituMesh, DISABLED_MappedMeshSourceRoundtrip)
     // TODO Add more comparison criteria
 
     ASSERT_TRUE(mesh != nullptr);
-    std::string test_data_file(
-        fs::temp_directory_path() /= BaseLib::random_string(32));
+    std::string test_data_file =
+        (fs::temp_directory_path() /= BaseLib::random_string(32)).string();
 
     // -- Test VtkMappedMeshSource, i.e. OGS mesh to VTK mesh
     vtkNew<MeshLib::VtkMappedMeshSource> vtkSource;