mcs 5 generates IL patterns that might lead to wrong behavior, if inlined, therefore we have to add another special case to the tests.

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -340,6 +340,14 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 			else if ((flags & CompilerOptions.UseMcsMask) != 0)
 			{
 				preprocessorSymbols.Add("MCS");
+				if (flags.HasFlag(CompilerOptions.UseMcs2_6_4))
+				{
+					preprocessorSymbols.Add("MCS2");
+				}
+				if (flags.HasFlag(CompilerOptions.UseMcs5_23))
+				{
+					preprocessorSymbols.Add("MCS5");
+				}
 			}
 			else
 			{

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Loops.cs

@@ -507,7 +507,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public void ForEachBreakWhenFound(string name, ref StringComparison output)
 		{
-#if MCS
+#if MCS2
 			foreach (int value in Enum.GetValues(typeof(StringComparison)))
 			{
 				if (((StringComparison)value).ToString() == name)
@@ -516,6 +516,16 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 					break;
 				}
 			}
+#elif MCS5
+			foreach (int value in Enum.GetValues(typeof(StringComparison)))
+			{
+				StringComparison stringComparison = (StringComparison)value;
+				if (stringComparison.ToString() == name)
+				{
+					output = (StringComparison)value;
+					break;
+				}
+			}
 #else
 			foreach (StringComparison value in Enum.GetValues(typeof(StringComparison)))
 			{