added .Unless extension method

some refactoring to make the code a bit more readable

Author: kkozmic

TestStack.ConventionTests/Internal/ConventionResult.cs

@@ -54,8 +54,8 @@ public void IsSymmetric<TResult>(
             Func<TResult, bool> isPartOfSecondSet,
             IEnumerable<TResult> allData)
         {
-            var firstSetFailingData = allData.Where(isPartOfFirstSet).Where(d => !isPartOfSecondSet(d));
-            var secondSetFailingData = allData.Where(d => !isPartOfFirstSet(d)).Where(isPartOfSecondSet);
+            var firstSetFailingData = allData.Where(isPartOfFirstSet).Unless(isPartOfSecondSet);
+            var secondSetFailingData = allData.Where(isPartOfSecondSet).Unless(isPartOfFirstSet);
 
             IsSymmetric(
                 firstSetFailureTitle, firstSetFailingData,

TestStack.ConventionTests/Internal/LinqExtensions.cs

@@ -1,6 +1,4 @@
-// ReSharper disable once CheckNamespace
-
-namespace TestStack.ConventionTests.Internal
+namespace TestStack.ConventionTests.Internal
 {
     using System;
     using System.Collections.Generic;
@@ -17,5 +15,11 @@ public static bool None<T>(this IEnumerable<T> enumerable, Func<T, bool> predica
         {
             return !enumerable.Any(predicate);
         }
+
+
+        public static IEnumerable<T> Unless<T>(this IEnumerable<T> enumerable, Func<T, bool> predicate)
+        {
+            return enumerable.Where(i => predicate(i) == false);
+        }
     }
 }