correct type to resolve new warning

Tests/Functional/Std/StandardTests.h

@@ -391,7 +391,7 @@ TEST_F(Std, MagneticSpheres)
 
 TEST_F(Std, MagneticCylinders)
 {
-    for (const std::string& polCase : {"PP", "MP", "PM", "MM"}) {
+    for (const auto polCase : {"PP", "MP", "PM", "MM"}) {
         std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createMagneticCylinders());
         auto sim = test::makeSimulation::MiniZPolarizedGISAS(*sample, polCase);
         EXPECT_TRUE(run("MagneticCylinders" + polCase, *sim, 2e-10));
@@ -400,7 +400,7 @@ TEST_F(Std, MagneticCylinders)
 
 TEST_F(Std, MagneticSpheresInMagLayer)
 {
-    for (const std::string& polCase : {"PP", "MP"}) {
+    for (const auto polCase : {"PP", "MP"}) {
         std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createMagneticLayer());
         auto sim = test::makeSimulation::MiniZPolarizedGISAS(*sample, polCase);
         EXPECT_TRUE(run("MagneticSpheresInMagLayer" + polCase, *sim, 2e-10));
@@ -650,7 +650,7 @@ TEST_F(Std, TOFResolutionComparison)
 TEST_F(Std, BasicSpecular)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createSimpleMagneticLayer());
-    for (const std::string& polCase : {"PP", "MM"}) {
+    for (const auto polCase : {"PP", "MM"}) {
         auto sim = test::makeSimulation::BasicYPolarizedSpecular(*sample, polCase, false);
         EXPECT_TRUE(run("BasicSpecular" + polCase, *sim, 1e-10));
     }
@@ -659,7 +659,7 @@ TEST_F(Std, BasicSpecular)
 TEST_F(Std, PolarizedQAngleReflectivity)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createSimpleMagneticLayer());
-    for (const std::string& polKey : {"PP", "MM"}) {
+    for (const auto polKey : {"PP", "MM"}) {
         auto sim = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
         EXPECT_TRUE(run("PolarizedQAngleReflectivity" + polKey + "_Q", *sim, 1e-10));
     }
@@ -667,10 +667,10 @@ TEST_F(Std, PolarizedQAngleReflectivity)
 
 TEST_F(Std, MagneticRotationReflectivity)
 {
-    for (const std::string& roughnessKey : {"Flat", "Tanh", "NevotCroce"}) {
+    for (const auto roughnessKey : {"Flat", "Tanh", "NevotCroce"}) {
         std::unique_ptr<const MultiLayer> sample(
             ExemplarySamples::createSimpleMagneticRotationWithRoughness(roughnessKey));
-        for (const std::string& polKey : {"PP", "PM", "MP", "MM"}) {
+        for (const auto polKey : {"PP", "PM", "MP", "MM"}) {
             auto sim = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
             EXPECT_TRUE(
                 run("MagneticRotationReflectivity" + polKey + "_" + roughnessKey, *sim, 1e-10));
@@ -681,7 +681,7 @@ TEST_F(Std, MagneticRotationReflectivity)
 TEST_F(Std, PolarizedFeNiBilayer)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayer());
-    for (const std::string& polKey : {"PP", "MM"}) {
+    for (const auto polKey : {"PP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayer" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
@@ -692,7 +692,7 @@ TEST_F(Std, PolarizedFeNiBilayer)
 TEST_F(Std, PolarizedFeNiBilayerTanh)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayerTanh());
-    for (const std::string& polKey : {"PP", "MM"}) {
+    for (const auto polKey : {"PP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayerTanh" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
@@ -703,7 +703,7 @@ TEST_F(Std, PolarizedFeNiBilayerTanh)
 TEST_F(Std, PolarizedFeNiBilayerNC)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayerNC());
-    for (const std::string& polKey : {"PP", "MM"}) {
+    for (const auto polKey : {"PP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayerNC" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
@@ -714,7 +714,7 @@ TEST_F(Std, PolarizedFeNiBilayerNC)
 TEST_F(Std, PolarizedFeNiBilayerSpinFlip)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayerSpinFlip());
-    for (const std::string& polKey : {"PP", "PM", "MP", "MM"}) {
+    for (const auto polKey : {"PP", "PM", "MP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayerSpinFlip" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
@@ -725,7 +725,7 @@ TEST_F(Std, PolarizedFeNiBilayerSpinFlip)
 TEST_F(Std, PolarizedFeNiBilayerSpinFlipTanh)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayerSpinFlipTanh());
-    for (const std::string& polKey : {"PP", "PM", "MP", "MM"}) {
+    for (const auto polKey : {"PP", "PM", "MP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayerSpinFlipTanh" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);
@@ -736,7 +736,7 @@ TEST_F(Std, PolarizedFeNiBilayerSpinFlipTanh)
 TEST_F(Std, PolarizedFeNiBilayerSpinFlipNC)
 {
     std::unique_ptr<const MultiLayer> sample(ExemplarySamples::createFeNiBilayerSpinFlipNC());
-    for (const std::string& polKey : {"PP", "PM", "MP", "MM"}) {
+    for (const auto polKey : {"PP", "PM", "MP", "MM"}) {
         auto sim1 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, false);
         EXPECT_TRUE(run("PolarizedFeNiBilayerSpinFlipNC" + polKey, *sim1, 1e-7));
         auto sim2 = test::makeSimulation::BasicYPolarizedSpecular(*sample, polKey, true);