Fix ambiguous header matching in fluent scanner for example tables (#289)

* - added a specific message

Added ArgumentException with a message to let user know that parameter name conflicts with header name in ExampleTable

* throw exception on ambiguous match for headers

* added unit tests for changes

---------

Co-authored-by: Fedor <[email protected]>

Author: SonOfSardaar

src/TestStack.BDDfy.Tests/Scanner/FluentScanner/AmbiguousHeaderMatchTests.cs

@@ -0,0 +1,33 @@
+using System.Reflection;
+using Shouldly;
+using Xunit;
+
+namespace TestStack.BDDfy.Tests.Scanner.FluentScanner
+{
+    public class AmbiguousHeaderMatchTests
+    {
+        private int _count;
+
+        [Fact]
+        public void ThrowsWhenMultipleHeadersMatchParameterName()
+        {
+            // Act & Assert
+            var exception = Should.Throw<AmbiguousMatchException>(() =>
+            {
+                this.Given(_ => GivenInput(_count))  // Will try to bind _count to both "count" and "Count" headers
+                    .WithExamples(new ExampleTable("count", "Count") // Deliberately ambiguous headers
+                    {
+                        { 5, 10 }
+                    })
+                    .BDDfy();
+            });
+
+            exception.Message.ShouldBe("More than one headers for examples, match the parameter 'count' provided for 'GivenInput'");
+        }
+
+        private void GivenInput(int count)
+        {
+            // The method exists just to trigger the ambiguous header match
+        }
+    }
+}

src/TestStack.BDDfy/Scanners/StepScanners/Fluent/FluentScanner.cs

@@ -203,9 +203,15 @@ private StepTitle CreateTitle(string stepTextTemplate, bool includeInputsInStepT
                                 {
                                     if (_testContext.Examples != null)
                                     {
-                                        var matchingHeader = _testContext.Examples.Headers
-                                            .SingleOrDefault(header => ExampleTable.HeaderMatches(header, i.ParameterName) ||
-                                            ExampleTable.HeaderMatches(header, i.Value.Name));
+                                        var matchingHeaders = _testContext.Examples.Headers
+                                            .Where(header => ExampleTable.HeaderMatches(header, i.ParameterName) ||
+                                                            ExampleTable.HeaderMatches(header, i.Value.Name))
+                                            .ToList();
+
+                                        if (matchingHeaders.Count > 1)
+                                            throw new AmbiguousMatchException ($"More than one headers for examples, match the parameter '{i.ParameterName}' provided for '{methodInfo.Name}'");
+
+                                        var matchingHeader = matchingHeaders.SingleOrDefault();
                                         if (matchingHeader != null)
                                             return string.Format("<{0}>", matchingHeader);
                                     }