Added a test for an ExcelFunctionProcessor applied to a standard function.

Author: Sergey-Vlasov

Source/Tests/ExcelDna.AddIn.RuntimeTests/ExclamationFunctionRegistration.cs

@@ -0,0 +1,24 @@
+using ExcelDna.Integration;
+using System.Linq.Expressions;
+
+namespace ExcelDna.AddIn.RuntimeTests
+{
+    internal static class ExclamationFunctionRegistration
+    {
+        [ExcelFunctionProcessor]
+        public static IEnumerable<IExcelFunctionInfo> ProcessExclamationFunctions(IEnumerable<IExcelFunctionInfo> registrations, IExcelFunctionRegistrationConfiguration config)
+        {
+            foreach (var reg in registrations)
+            {
+                if (reg.FunctionAttribute.Name == "MySayHelloWithExclamation")
+                {
+                    var concatMethod = typeof(string).GetMethod("Concat", new[] { typeof(string), typeof(string) });
+                    var newBody = Expression.Call(concatMethod!, reg.FunctionLambda.Body, Expression.Constant("!"));
+                    reg.FunctionLambda = Expression.Lambda<Func<string, string>>(newBody, reg.FunctionLambda.Parameters);
+                }
+
+                yield return reg;
+            }
+        }
+    }
+}

Source/Tests/ExcelDna.AddIn.RuntimeTests/MyFunctions.cs

@@ -13,6 +13,12 @@ public static string SayHello(string name)
             return $"Hello {name}";
         }
 
+        [ExcelFunction]
+        public static string MySayHelloWithExclamation(string name)
+        {
+            return $"Hello with exclamation {name}";
+        }
+
         [ExcelFunction, Logging(7)]
         public static string SayHelloWithLoggingID(string name)
         {

Source/Tests/ExcelDna.RuntimeTests/Registration.cs

@@ -14,6 +14,14 @@ public void SayHello()
             Assert.Equal("Hello world", functionRange.Value.ToString());
         }
 
+        [ExcelFact(Workbook = "", AddIn = @"..\..\..\..\ExcelDna.AddIn.RuntimeTests\bin\Debug\net6.0-windows\ExcelDna.AddIn.RuntimeTests-AddIn")]
+        public void ExclamationFunctionProcessor()
+        {
+            Range functionRange = ((Worksheet)ExcelDna.Testing.Util.Workbook.Sheets[1]).Range["B1:B1"];
+            functionRange.Formula = "=MySayHelloWithExclamation(\"world ex\")";
+            Assert.Equal("Hello with exclamation world ex!", functionRange.Value.ToString());
+        }
+
         [ExcelFact(Workbook = "", AddIn = @"..\..\..\..\ExcelDna.AddIn.RuntimeTests\bin\Debug\net6.0-windows\ExcelDna.AddIn.RuntimeTests-AddIn")]
         public void Double()
         {