[T|TestFixedTimeStepping] Check special setting

The setting was provided by a user and didn't work properly. With the
previous commits it works now.

Tests/NumLib/TestFixedTimeStepping.cpp

@@ -142,3 +142,56 @@ TEST_F(NumLibFixedTimeStepping, next)
     ac::check<std::vector<double>>(
         test, 1000, time_points, gtest_reporter, double_classifier);
 }
+
+TEST_F(NumLibFixedTimeStepping, next_StaticTest)
+{
+    std::vector<double> expected_time_points{};
+    for (int i = 0; i < 101; ++i)
+    {
+        expected_time_points.push_back(i * 1e-2);
+    }
+
+    std::vector<double> fixed_output_times{};
+    for (int i = 0; i < 10; ++i)
+    {
+        fixed_output_times.push_back(i * 1e-1);
+    }
+
+    double const t_initial = expected_time_points.front();
+
+    expected_time_points.erase(expected_time_points.begin());
+
+    double const t_end = expected_time_points.back();
+    auto dts = transformTimesToDts(expected_time_points);
+    dts.front() -= t_initial;
+    auto const repeat_dt_pair = transformToRepeatDtPair(dts);
+    NumLib::FixedTimeStepping fixed_time_stepping{
+        t_initial, t_end, repeat_dt_pair, fixed_output_times};
+
+    NumLib::TimeStep ts_dummy(0, 0, 0);
+    NumLib::TimeStep ts_current(0, t_initial, 0);
+    for (auto const& expected_time_point : expected_time_points)
+    {
+        auto [is_next, step_size] =
+            fixed_time_stepping.next(0.0 /* solution_error */,
+                                     0 /* number_of_iterations */,
+                                     ts_dummy,
+                                     ts_current);
+        // this only happens if the last time step was processed or the
+        // current time is already at the end time up to machine precision
+        ASSERT_FALSE(!is_next && step_size != 0.0);
+
+        // if the current time plus the computed step size minus the
+        // expected time is larger than the minimal time step size then the
+        // step size should be larger
+        // if next is true then the step
+        ASSERT_FALSE(is_next && std::abs((ts_current.current() + step_size) -
+                                         expected_time_point) >
+                                    NumLib::TimeStep::minimalTimeStepSize);
+
+        // if next is true then the step size should be larger than zero
+        ASSERT_FALSE(is_next && step_size == 0.0);
+        ts_current += step_size;
+    }
+    ASSERT_EQ(ts_current.timeStepNumber(), dts.size());
+}