added test for ticket-5206

Belonging to [master]:
  - OpenModelica/OpenModelica-testsuite#1071

simulation/modelica/equations/Makefile

@@ -23,6 +23,7 @@ IfEquation6.mos \
 IfEquationUnbalanced.mos \
 ModelBalance1.mos ModelBalance2.mos ModelBalance3.mos ModelBalance4.mos \
 ticket-2337.mos \
+ticket-5206.mos \
 WatchDog1AlgorithmWhen.mos WatchDog2EquationWhen.mos \
 WhenEquation.mos WhenEquation1.mos \
 WhenNoRetCall.mos \

simulation/modelica/equations/ticket-5206.mos

@@ -0,0 +1,56 @@
+// name: ticket-5206
+// keywords: if equations, non-linear, residual equations
+// status: correct
+
+
+loadString("
+model Test5206
+  Real x(start=1);
+  Real y(start=8);
+  Real usat(start=1);
+  Real u(start=2);
+  parameter Real y0(fixed = false, start = 8);
+  parameter Real T = 1;
+  parameter Real k = 10;
+  parameter Real uMin = 0;
+  parameter Real uMax = 1;
+  parameter Real y_ref = 8;
+initial equation
+  der(x) = 0;
+  if u > usat then
+    u = usat + 1;
+  else
+    y = y_ref;
+  end if;
+equation
+  T * der(x) = usat - x;
+  y = k * x;
+  usat = homotopy(actual = smooth(0, if u > uMax then uMax else if u < uMin then uMin else u), simplified = u);
+  u = y0 - y;
+end Test5206;
+");
+getErrorString();
+
+simulate(Test5206);
+getErrorString();
+
+val(x,0.0);
+val(x,1.0);
+
+// Result:
+// true
+// ""
+//
+// The selection of a new tearing variable failed.
+// record SimulationResult
+//     resultFile = "Test5206_res.mat",
+//     simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 1e-06, method = 'dassl', fileNamePrefix = 'Test5206', options = '', outputFormat = 'mat', variableFilter = '.*', cflags = '', simflags = ''",
+//     messages = "LOG_SUCCESS       | info    | The initialization finished successfully without homotopy method.
+// LOG_SUCCESS       | info    | The simulation finished successfully.
+// "
+// end SimulationResult;
+// "Warning: Function Tearing.selectTearingVar failed at least once. Use -d=tearingdump or -d=tearingdumpV for more information.
+// "
+// 1.0
+// 1.0
+// endResult