Fix TableFormula error message to show existing Y value (#2778)

* Initial plan

* Fix TableFormula error message to show existing Y value

Co-authored-by: PavelBal <25903040+PavelBal@users.noreply.github.com>

* Improve test assertion to ensure exception is thrown

Co-authored-by: PavelBal <25903040+PavelBal@users.noreply.github.com>

* Use existing constructor with existingPoint instead of adding new overload

Co-authored-by: rwmcintosh <261477+rwmcintosh@users.noreply.github.com>

* refactor the test to make it compile and work.

* add a comment in the test.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: PavelBal <25903040+PavelBal@users.noreply.github.com>
Co-authored-by: rwmcintosh <261477+rwmcintosh@users.noreply.github.com>

Author: 3 people

src/OSPSuite.Core/Domain/Formulas/TableFormula.cs

@@ -224,7 +224,7 @@ public virtual int AddPoint(ValuePoint point)
             if (existingPoint.Y == point.Y)
                return index;
 
-            throw new ValuePointAlreadyExistsForPointException(point);
+            throw new ValuePointAlreadyExistsForPointException(existingPoint);
          }
 
          //does not exist

tests/OSPSuite.Core.Tests/Domain/TableFormulaSpecs.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using FakeItEasy;
 using OSPSuite.BDDHelper;
@@ -143,6 +144,29 @@ public void should_throw_an_exception()
       {
          The.Action(() => sut.AddPoint(2, 30)).ShouldThrowAn<ValuePointAlreadyExistsForPointException>();
       }
+
+      [Observation]
+      public void should_throw_an_exception_with_the_existing_y_value_in_the_message()
+      {
+         Exception exception = null;
+         The.Action(() =>
+         {
+            try
+            {
+               sut.AddPoint(2, 30);
+            }
+            catch (Exception e)
+            {
+               // capture the message to verify that the new coordinate is used.
+               exception = e;
+               throw;
+            }
+            
+         }).ShouldThrowAn<ValuePointAlreadyExistsForPointException>();
+
+         exception.Message.Contains("x=2").ShouldBeTrue();
+         exception.Message.Contains("y=20").ShouldBeTrue(); // The existing Y value, not the new one (30)
+      }
    }
 
    public class When_clearing_all_points_from_a_table_formula : concern_for_TableFormula