[test.validation] using integer limits provoked test failure

dune/xt/common/test/validation.cc

@@ -42,19 +42,16 @@ struct ValidationTest : public testing::Test
   void all()
   {
     using namespace boost::assign;
-    const int samples = 100;
-    std::cout << "\tTesting Validators for type " << Typename<T>::value() << "\n\t\t" << samples
-              << " random numbers ..." << std::endl;
     {
       typedef VectorAbstraction<T>::S S;
       const auto scalar_eps = Epsilon<S>::value;
-      const T lower = init_bound<T>(std::numeric_limits<S>::min() + scalar_eps);
-      const T upper = init_bound<T>(std::numeric_limits<S>::max() - scalar_eps);
-      RNGType rng(lower, upper);
-      for (int i = samples; i > 0; --i) {
-        const T arg = rng();
+      const T lower = init_bound<T>(std::numeric_limits<S>::min() / 6 + scalar_eps);
+      const T upper = init_bound<T>(std::numeric_limits<S>::max() / 6 - scalar_eps);
+
+      for (auto&& arg : std::array<T, 3>{{lower, T(0), upper}}) {
         test(lower, upper, arg);
       }
+      RNGType rng(lower, upper);
       boost::array<T, 10> ar = list_of<T>().repeat_fun(9, rng);
       ValidateInList<T, boost::array<T, 10>> validator(ar);
       for (T t : ar) {

dune/xt/common/validation.hh

@@ -108,7 +108,7 @@ public:
   }
 };
 
-//! validate arg iff less than value, obviously
+//! validate arg iff lhs < rhs
 template <class T>
 class ValidateLess : public ValidatorInterface<T, ValidateLess<T>>
 {
@@ -131,7 +131,7 @@ private:
   const T lhs_;
 };
 
-//! validate arg iff greater than value, obviously
+//! validate arg iff lhs > rhs, obviously
 template <class T>
 class ValidateGreater : public ValidatorInterface<T, ValidateGreater<T>>
 {