diff --git a/test/common/functionfromstringexpression/test_functionfromstringexpression.cc b/test/common/functionfromstringexpression/test_functionfromstringexpression.cc
index e97865af37d9f3942047517ade83793e3067ad39..9c75c93add0249dd84421f838f28415019355520 100644
--- a/test/common/functionfromstringexpression/test_functionfromstringexpression.cc
+++ b/test/common/functionfromstringexpression/test_functionfromstringexpression.cc
@@ -70,7 +70,7 @@ int main(int argc, char* argv[])
         const std::string funcStr = "foo*sin(bar)*bla";
         bool error = false;
         try { FunctionFromStringExpression<2> func(funcStr, std::array<std::string, 2>{{"foo" "bar"}}); }
-        catch (Dune::IOError& e) { error = true; }
+        catch (const Dune::IOError& e) { error = true; }
         if (!error)
             DUNE_THROW(Dune::Exception, "Faulty expression did not throw: " << funcStr);
     }
diff --git a/test/common/spline/test_spline.cc b/test/common/spline/test_spline.cc
index 30249beeb237ed030bfe2dca1aea8c79bebe46b4..10f8a086f19d0fd23d2348a497c359fe8e299a1a 100644
--- a/test/common/spline/test_spline.cc
+++ b/test/common/spline/test_spline.cc
@@ -240,8 +240,8 @@ void plot()
     double y_[] = { 10, 0, 10, 0, 10 };
     double m1 = 10;
     double m2 = -10;
-    FV &xs = *reinterpret_cast<FV*>(x_);
-    FV &ys = *reinterpret_cast<FV*>(y_);
+    const FV &xs = *reinterpret_cast<FV*>(x_);
+    const FV &ys = *reinterpret_cast<FV*>(y_);
 
     Dumux::Spline<double, numSamples> spFull(xs, ys, m1, m2);
     Dumux::Spline<double, numSamples> spNatural(xs, ys);
diff --git a/test/geometry/test_1d2d_intersection.cc b/test/geometry/test_1d2d_intersection.cc
index d4cf483f194350337b9e38d21f4453f9b9709500..0deac74958710f914ddb1faf1f73def390d956c9 100644
--- a/test/geometry/test_1d2d_intersection.cc
+++ b/test/geometry/test_1d2d_intersection.cc
@@ -26,7 +26,7 @@ Dune::MultiLinearGeometry<double, 1, 3>
 makeLine(std::initializer_list<Dune::FieldVector<double, 2>>&& c, std::integral_constant<int, 3>)
 {
     std::vector<Dune::FieldVector<double, 3>> corners;
-    for (auto& corner : c)
+    for (const auto& corner : c)
     {
         Dune::FieldVector<double, 3> coord;
         coord[0] = corner[0];