diff --git a/tests/fff_print/test_flow.cpp b/tests/fff_print/test_flow.cpp
index 810e97729..36ff3c7e7 100644
--- a/tests/fff_print/test_flow.cpp
+++ b/tests/fff_print/test_flow.cpp
@@ -33,7 +33,7 @@ SCENARIO("Extrusion width specifics", "[!mayfail]") {
             std::vector<double> E_per_mm_bottom;
             std::string gcode = Test::gcode(print);
             Slic3r::GCodeReader parser;
-            const auto layer_height { config->opt_float("layer_height") };
+            const double layer_height = config->opt_float("layer_height");
             parser.parse_buffer(gcode, [&E_per_mm_bottom, layer_height] (Slic3r::GCodeReader& self, const Slic3r::GCodeReader::GCodeLine& line)
             { 
                 if (self.z() == Approx(layer_height).margin(0.01)) { // only consider first layer
@@ -44,7 +44,7 @@ SCENARIO("Extrusion width specifics", "[!mayfail]") {
             });
             THEN(" First layer width applies to everything on first layer.") {
                 bool pass = false;
-                auto avg_E {std::accumulate(E_per_mm_bottom.cbegin(), E_per_mm_bottom.cend(), 0.0) / static_cast<double>(E_per_mm_bottom.size())};
+                double avg_E = std::accumulate(E_per_mm_bottom.cbegin(), E_per_mm_bottom.cend(), 0.0) / static_cast<double>(E_per_mm_bottom.size());
 
                 pass = (std::count_if(E_per_mm_bottom.cbegin(), E_per_mm_bottom.cend(), [avg_E] (const double& v) { return v == Approx(avg_E); }) == 0);
                 REQUIRE(pass == true);
@@ -91,7 +91,7 @@ SCENARIO(" Bridge flow specifics.", "[!mayfail]") {
 /// spacing, etc
 SCENARIO("Flow: Flow math for non-bridges", "[!mayfail]") {
     GIVEN("Nozzle Diameter of 0.4, a desired width of 1mm and layer height of 0.5") {
-        auto width {ConfigOptionFloatOrPercent(1.0, false)};
+        ConfigOptionFloatOrPercent width(1.0, false);
         float spacing {0.4};
         float nozzle_diameter {0.4};
         float bridge_flow {1.0};
@@ -99,16 +99,16 @@ SCENARIO("Flow: Flow math for non-bridges", "[!mayfail]") {
 
         // Spacing for non-bridges is has some overlap
         THEN("External perimeter flow has spacing fixed to 1.1*nozzle_diameter") {
-            auto flow {Flow::new_from_config_width(frExternalPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f)};
+            auto flow = Flow::new_from_config_width(frExternalPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f);
             REQUIRE(flow.spacing() == Approx((1.1*nozzle_diameter) - layer_height * (1.0 - PI / 4.0)));
         }
 
         THEN("Internal perimeter flow has spacing of 1.05 (minimum)") {
-            auto flow {Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f)};
+            auto flow = Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f);
             REQUIRE(flow.spacing() == Approx((1.05*nozzle_diameter) - layer_height * (1.0 - PI / 4.0)));
         }
         THEN("Spacing for supplied width is 0.8927f") {
-            auto flow {Flow::new_from_config_width(frExternalPerimeter, width, nozzle_diameter, layer_height, 0.0f)};
+            auto flow = Flow::new_from_config_width(frExternalPerimeter, width, nozzle_diameter, layer_height, 0.0f);
             REQUIRE(flow.spacing() == Approx(width.value - layer_height * (1.0 - PI / 4.0)));
             flow = Flow::new_from_config_width(frPerimeter, width, nozzle_diameter, layer_height, 0.0f);
             REQUIRE(flow.spacing() == Approx(width.value - layer_height * (1.0 - PI / 4.0)));
@@ -123,14 +123,14 @@ SCENARIO("Flow: Flow math for non-bridges", "[!mayfail]") {
         WHEN("layer height is set to 0.2") {
             layer_height = 0.15f;
             THEN("Max width is set.") {
-                auto flow {Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f)};
+                auto flow = Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f);
                 REQUIRE(flow.width == Approx(1.4*nozzle_diameter));
             }
         }
         WHEN("Layer height is set to 0.2") {
             layer_height = 0.3f;
             THEN("Min width is set.") {
-                auto flow {Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f)};
+                auto flow = Flow::new_from_config_width(frPerimeter, ConfigOptionFloatOrPercent(0, false), nozzle_diameter, layer_height, 0.0f);
                 REQUIRE(flow.width == Approx(1.05*nozzle_diameter));
             }
         }
@@ -143,7 +143,7 @@ SCENARIO("Flow: Flow math for non-bridges", "[!mayfail]") {
     GIVEN("Input spacing of 0.414159 and a total width of 2") {
         double in_spacing = 0.414159;
         double total_width = 2.0;
-        auto flow {Flow::new_from_spacing(1.0, 0.4, 0.3, false)};
+        auto flow = Flow::new_from_spacing(1.0, 0.4, 0.3, false);
         WHEN("solid_spacing() is called") {
             double result = flow.solid_spacing(total_width, in_spacing);
             THEN("Yielded spacing is greater than 0") {
@@ -158,13 +158,13 @@ SCENARIO("Flow: Flow math for non-bridges", "[!mayfail]") {
 /// Spacing, width calculation for bridge extrusions
 SCENARIO("Flow: Flow math for bridges", "[!mayfail]") {
     GIVEN("Nozzle Diameter of 0.4, a desired width of 1mm and layer height of 0.5") {
-        auto width {ConfigOptionFloatOrPercent(1.0, false)};
-        auto spacing {0.4};
-        auto nozzle_diameter {0.4};
-        auto bridge_flow {1.0};
-        auto layer_height {0.5};
+        auto width = ConfigOptionFloatOrPercent(1.0, false);
+        double spacing = 0.4;
+        double nozzle_diameter = 0.4;
+        double bridge_flow = 1.0;
+        double layer_height = 0.5;
         WHEN("Flow role is frExternalPerimeter") {
-            auto flow {Flow::new_from_config_width(frExternalPerimeter, width, nozzle_diameter, layer_height, bridge_flow)};
+            auto flow = Flow::new_from_config_width(frExternalPerimeter, width, nozzle_diameter, layer_height, bridge_flow);
             THEN("Bridge width is same as nozzle diameter") {
                 REQUIRE(flow.width == Approx(nozzle_diameter));
             }
@@ -173,7 +173,7 @@ SCENARIO("Flow: Flow math for bridges", "[!mayfail]") {
             }
         }
         WHEN("Flow role is frInfill") {
-            auto flow {Flow::new_from_config_width(frInfill, width, nozzle_diameter, layer_height, bridge_flow)};
+            auto flow = Flow::new_from_config_width(frInfill, width, nozzle_diameter, layer_height, bridge_flow);
             THEN("Bridge width is same as nozzle diameter") {
                 REQUIRE(flow.width == Approx(nozzle_diameter));
             }
@@ -182,7 +182,7 @@ SCENARIO("Flow: Flow math for bridges", "[!mayfail]") {
             }
         }
         WHEN("Flow role is frPerimeter") {
-            auto flow {Flow::new_from_config_width(frPerimeter, width, nozzle_diameter, layer_height, bridge_flow)};
+            auto flow = Flow::new_from_config_width(frPerimeter, width, nozzle_diameter, layer_height, bridge_flow);
             THEN("Bridge width is same as nozzle diameter") {
                 REQUIRE(flow.width == Approx(nozzle_diameter));
             }
@@ -191,7 +191,7 @@ SCENARIO("Flow: Flow math for bridges", "[!mayfail]") {
             }
         }
         WHEN("Flow role is frSupportMaterial") {
-            auto flow {Flow::new_from_config_width(frSupportMaterial, width, nozzle_diameter, layer_height, bridge_flow)};
+            auto flow = Flow::new_from_config_width(frSupportMaterial, width, nozzle_diameter, layer_height, bridge_flow);
             THEN("Bridge width is same as nozzle diameter") {
                 REQUIRE(flow.width == Approx(nozzle_diameter));
             }